:root {
  --bb-green: #adc276; --bb-green-dark: #8da45a; --bb-green-deep: #5d7139;   /* links and small print: 5.4:1 on white */
  --bb-dark: #111111; --bb-secondary: #5f6b57; --bb-sage: #bbd291; --bb-border: #c9d6aa;
  --bb-light-bg: #e2ecce; --bb-red: #d9534f; --bb-red-bg: #f7dcdb; --bb-amber: #e0a800;
  --bb-cream: #ffffff; --bb-green-light: #bbd291; --bb-yellow: #fdd14d;
  /* every surface goes through a name, so the dark theme is a list of colours and nothing else */
  --bb-surface: #ffffff;        /* cards, panels, popups, buttons */
  --bb-code-bg: #ffffff;        /* the editor and the console */
  --bb-view-bg: #faf8ef;        /* around the robot's mat */
  --bb-bar: var(--bb-green);    /* the top bar */
  --bb-soft: #f4f7ee;           /* the bars that belong to a cell: debug, share */
  --bb-note: #fff7d6;           /* a note from the teacher */
  --bb-note-border: #e8d48a;
  --bb-ink-dim: #3d4a30;        /* small print on a green ground */
  --bb-placeholder: #9aa7ad;
  --bb-red-ink: #7a1f1b;
  --bb-cam-bg: #c9d3c3;         /* behind the robot's camera view, which is drawn on a clear canvas */
  --bb-chip: rgba(255,255,255,.65);   /* a word of code sitting on a coloured ground */
  --bb-on-green: #111111;       /* the brand green is light in both themes: what sits on it never changes */
  --bb-on-green-dim: #3d4a30;
  /* one scale for the whole page: rem sizes everything, including the code */
  --text-scale: 1;
  --code-size: .84rem;
}
/* the student's text size: the page is laid out in rem, so this moves all of it at once */
html { font-size: calc(100% * var(--text-scale)); }

/* the dark theme: the same page, a different set of colours */
:root.bb-dark {
  --bb-dark: #e4e8ec; --bb-secondary: #9fb2bf; --bb-border: #2b323a;
  --bb-cream: #14171b; --bb-surface: #1b1f25; --bb-code-bg: #15181c; --bb-view-bg: #101317;
  --bb-light-bg: #222932; --bb-sage: #232a31; --bb-bar: #1b2026; --bb-soft: #1e242b;
  --bb-note: #2c2718; --bb-note-border: #5b4f29; --bb-ink-dim: #b6c4cf; --bb-placeholder: #66727d;
  --bb-green-deep: #a8e06a; --bb-red: #ff8a84; --bb-red-bg: #3a2322; --bb-red-ink: #ffb4ae;
  --bb-cam-bg: #232a28; --bb-chip: rgba(255,255,255,.12);
  color-scheme: dark;
}
* { box-sizing: border-box; }
html, body { margin: 0; min-height: 100%; }
body { font-family: 'Nunito', system-ui, sans-serif; color: var(--bb-dark); background: var(--bb-cream); line-height: 1.55; }
a { color: var(--bb-green-deep); }

/* top bar: cream, the wordmark logo, the site's name beside it */
.bar { position: sticky; top: 0; z-index: 20; display: flex; align-items: center; gap: 1.5rem; padding: .45rem 1.25rem; background: var(--bb-bar); color: var(--bb-dark); }
.brand { font-family: 'Varela Round', sans-serif; font-size: 1.05rem; color: var(--bb-dark); text-decoration: none; display: flex; align-items: center; gap: .7rem; }
.brand .logo { height: 38px; width: auto; display: inline-block; }
.brand .site { padding: .15rem .65rem; border-radius: 999px; background: #000; color: #fff; font-size: .85rem; font-weight: 700; letter-spacing: .02em; }
.bar-links { display: flex; gap: 1.1rem; margin-left: auto; }
.bar-links a { color: var(--bb-dark); text-decoration: none; font-weight: 700; font-size: .9rem; }
.bar-links a:hover { color: #fff; }
.status { font-family: 'Roboto Mono', monospace; font-size: .75rem; color: var(--bb-ink-dim); }

/* the one WebGL canvas: fixed over the page, drawn only inside visible cells */
/* the shared WebGL canvas is a scratch surface: each view is copied into the cell's own canvas, which scrolls with the page */
.gl { position: fixed; inset: 0; width: 100%; height: 100%; pointer-events: none; visibility: hidden; z-index: -1; }

/* index */
.index { max-width: 1000px; margin: 0 auto; padding: 2.5rem 1.25rem 4rem; }
.index h1 { font-family: 'Varela Round', sans-serif; font-weight: 400; font-size: 2rem; margin: 0 0 .5rem; }
.index .lead { color: var(--bb-secondary); max-width: 62ch; margin-bottom: 2rem; }
.module { margin-bottom: 2.5rem; }
.module-head { display: flex; align-items: flex-start; justify-content: space-between; gap: 1rem; margin-bottom: 1rem; }
.module-head .num { font-family: 'Roboto Mono', monospace; font-size: .75rem; color: var(--bb-secondary); letter-spacing: .05em; }
.module-head h2 { font-family: 'Varela Round', sans-serif; font-weight: 400; margin: .2rem 0 .3rem; font-size: 1.5rem; }
.module-head p { margin: 0; color: var(--bb-secondary); max-width: 62ch; }
.side-module { margin-bottom: .35rem; }
.side-module-title { display: flex; align-items: center; gap: .4rem; width: 100%; text-align: left; font-size: .72rem; letter-spacing: .06em; text-transform: uppercase; color: var(--bb-secondary); margin: .35rem 0 .1rem; padding: .3rem 0; border: 0; background: none; border-radius: 4px; font-weight: 700; }
.side-module-title:hover { background: var(--bb-light-bg); }
.side-module-title .t { flex: 1; }
.side-module-title .count { font-family: 'Roboto Mono', monospace; font-size: .7rem; text-transform: none; letter-spacing: 0; }
.side-module-title .chev { width: 0; height: 0; border-left: 5px solid transparent; border-right: 5px solid transparent; border-top: 6px solid var(--bb-secondary); transform: rotate(-90deg); transition: transform .15s; }
.side-module.open .side-module-title .chev { transform: rotate(0); }
.side-module-body { display: none; padding-left: .9rem; }
.side-module.open .side-module-body { display: block; }
.drawer-toggle { display: none; }
.drawer-backdrop { display: none; }
.crumb { font-size: .8rem; color: var(--bb-secondary); letter-spacing: .03em; margin-top: .5rem; }
.lesson-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(280px, 1fr)); gap: 1.25rem; }
.lesson-card { display: block; text-decoration: none; color: inherit; border: 1px solid var(--bb-border); border-radius: 12px; padding: 1.25rem 1.25rem 1rem; background: var(--bb-surface); transition: box-shadow .15s; }
.lesson-card:hover { box-shadow: 0 .5rem 1.5rem rgba(0,0,0,.08); }
.lesson-card .num { font-family: 'Roboto Mono', monospace; font-size: .75rem; color: var(--bb-secondary); letter-spacing: .05em; }
.lesson-card h3 { font-family: 'Varela Round', sans-serif; font-weight: 400; margin: .25rem 0 .4rem; font-size: 1.2rem; }
.lesson-card p { margin: 0 0 .75rem; color: var(--bb-secondary); font-size: .95rem; }
.lesson-card .meta { display: flex; justify-content: space-between; align-items: center; font-size: .8rem; color: var(--bb-secondary); }
.progress-pill { border-radius: 999px; padding: .15rem .6rem; font-weight: 700; font-size: .75rem; background: var(--bb-light-bg); border: 1px solid var(--bb-border); }
.progress-pill.done { background: var(--bb-green); border-color: var(--bb-green); color: var(--bb-on-green); }

/* lesson layout */
.lesson { display: grid; grid-template-columns: 250px minmax(0, 1fr); gap: 2.5rem; max-width: 1180px; margin: 0 auto; padding: 1.5rem 1.25rem 0; }
/* anchors and scrolled cells stop below the sticky bar */
html { scroll-padding-top: 3.6rem; }
.cell { scroll-margin-top: 3.6rem; }
.side { position: sticky; top: 3.4rem; align-self: start; max-height: calc(100vh - 3.4rem); overflow: auto; padding-top: .75rem; font-size: .9rem; }
.side h4 { margin: 1rem 0 .4rem; font-size: .75rem; letter-spacing: .08em; text-transform: uppercase; color: var(--bb-secondary); }
.side a { display: block; text-decoration: none; color: var(--bb-dark); padding: .25rem 0; }
.side a.current { color: var(--bb-green-deep); font-weight: 700; }
.side .outline a { color: var(--bb-secondary); padding-left: .5rem; border-left: 2px solid var(--bb-border); }
.side .outline a.active { color: var(--bb-dark); border-left-color: var(--bb-green-dark); }
.main { min-width: 0; max-width: 760px; padding-bottom: 5rem; }
.main h1 { font-family: 'Varela Round', sans-serif; font-weight: 400; font-size: 2.1rem; margin: .5rem 0 1rem; text-wrap: balance; }
.main h2 { font-family: 'Varela Round', sans-serif; font-weight: 400; font-size: 1.45rem; margin: 2.4rem 0 .6rem; padding-top: .5rem; scroll-margin-top: 4.5rem; }
.main p, .main li { max-width: 68ch; }
.main code { font-family: 'Roboto Mono', monospace; font-size: .88em; background: var(--bb-light-bg); border: 1px solid var(--bb-border); border-radius: 3px; padding: 0 .25em; }
.main pre { background: var(--bb-light-bg); border: 1px solid var(--bb-border); border-radius: 8px; padding: .8rem 1rem; overflow-x: auto; font-family: 'Roboto Mono', monospace; font-size: .85rem; line-height: 1.5; }
.main pre code { background: none; border: 0; padding: 0; font-size: inherit; }
.main ol li, .main ul li { margin: .3rem 0; }
.main h2.quiz-title { margin-top: 2.5rem; }

/* a file of the student's own on a lesson page: an editor with no robot, which the page's cells can import */
.file-cell .cell-head { grid-template-columns: auto minmax(0, 1fr) auto; }
.file-cell .cell-head .note { font-size: .78rem; color: var(--bb-ink-dim); min-width: 0; }
.file-cell .file-reset { font: inherit; font-size: .78rem; padding: .2rem .6rem; }
.file-cell .CodeMirror { height: auto; font-size: var(--code-size); }
.file-cell.file-written .cell-head { animation: file-written 1.6s ease-out; }
@keyframes file-written { from { background: var(--bb-yellow); } to { background: var(--bb-sage); } }
@media (prefers-reduced-motion: reduce) { .file-cell.file-written .cell-head { animation: none; outline: 2px solid var(--bb-yellow); } }

/* the same files as tabs on a cell, so a file can be read without scrolling back up the page */
.cell .file-bar { display: flex; align-items: center; gap: .15rem; padding: 0 .55rem; background: var(--bb-code-bg); border-bottom: 1px solid var(--bb-border); overflow-x: auto; overflow-y: hidden; scrollbar-width: thin; }
.cell .file-tab { font: inherit; font-size: .78rem; padding: .35rem .5rem; border: 0; border-bottom: 2px solid transparent; background: transparent; color: var(--bb-secondary); cursor: pointer; white-space: nowrap; margin-bottom: -1px; }
.cell .file-tab:hover { color: var(--bb-dark); }
.cell .file-tab.on { color: var(--bb-dark); font-weight: 600; border-bottom-color: var(--bb-green-dark); }
.cell .file-actions { margin-left: auto; display: flex; align-items: center; gap: .4rem; padding-left: .5rem; }
.cell .file-bar .file-reset { font: inherit; font-size: .75rem; padding: .15rem .5rem; white-space: nowrap; }
.cell .file-add { font: inherit; font-size: .75rem; padding: .15rem .4rem; border: 0; background: transparent; color: var(--bb-secondary); cursor: pointer; white-space: nowrap; }
.cell .file-add:hover { color: var(--bb-dark); text-decoration: underline; }
.cell .file-tab.file-written { animation: file-written 1.6s ease-out; }
@media (prefers-reduced-motion: reduce) { .cell .file-tab.file-written { animation: none; outline: 2px solid var(--bb-yellow); } }

/* a flowchart drawn inline: its lines and words follow the text colour, so it works in both themes */
.main figure.flowchart { margin: 1.4rem 0; max-width: 68ch; color: var(--bb-dark); }
.main figure.flowchart svg { display: block; width: 100%; height: auto; max-height: 34rem; }
.main figure.flowchart figcaption { font-size: .8rem; color: var(--bb-secondary); margin-top: .35rem; }

/* an exam box: what the exam boards expect on this topic, one tab per board */
.exam { margin: 1.6rem 0; max-width: 68ch; border: 1px solid var(--bb-border); border-radius: 10px; background: var(--bb-surface); overflow: hidden; }
.exam-head { display: flex; flex-wrap: wrap; align-items: center; justify-content: space-between; gap: .5rem .75rem; padding: .4rem .5rem .4rem .9rem; background: var(--bb-soft); border-bottom: 1px solid var(--bb-border); }
.exam-title { font-size: .75rem; font-weight: 700; letter-spacing: .07em; text-transform: uppercase; color: var(--bb-secondary); }
.exam-boards { display: flex; gap: .25rem; }
.exam-boards button { font: inherit; font-size: .8rem; line-height: 1.2; padding: .22rem .7rem; border-radius: 999px; border: 1px solid var(--bb-border); background: var(--bb-surface); color: var(--bb-dark); cursor: pointer; }
.exam-boards button:hover { border-color: var(--bb-green-dark); }
.exam-boards button[aria-selected="true"] { background: var(--bb-green); border-color: var(--bb-green); color: var(--bb-on-green); font-weight: 700; }
.exam-boards button:focus-visible { outline: 2px solid var(--bb-green-deep); outline-offset: 2px; }
.exam-body { padding: .1rem 1rem .5rem; }
.exam-body > :first-child, .exam-board > :first-child { margin-top: .6rem; }
.exam-spec { font-family: 'Roboto Mono', monospace; font-size: .72rem; letter-spacing: .02em; color: var(--bb-secondary); margin: .7rem 0 -.2rem; }
.exam-body pre { font-size: .8rem; }
.quiz-lead { color: var(--bb-secondary); }
.quiz-q { margin: 1rem 0; padding: .8rem 1rem; border: 1px solid var(--bb-border); border-radius: 10px; background: var(--bb-surface); }
.quiz-q.right { border-color: var(--bb-green-dark); box-shadow: inset 4px 0 var(--bb-green-dark); }
.quiz-q.wrong { border-color: var(--bb-red); box-shadow: inset 4px 0 var(--bb-red); }
.quiz-q fieldset { border: 0; margin: 0; padding: 0; min-width: 0; }
.quiz-q legend { font-weight: 700; padding: 0; margin-bottom: .5rem; }
.quiz-q legend code, .quiz-options code, .quiz-explain code { font-family: 'Roboto Mono', monospace; font-size: .9em; background: var(--bb-light-bg); padding: 0 .3em; border-radius: 3px; font-weight: 500; }
.quiz-n { display: inline-flex; align-items: center; justify-content: center; min-width: 1.6rem; height: 1.6rem; margin-right: .3rem; border-radius: 50%; background: var(--bb-sage); color: var(--bb-on-green); font-size: .85rem; }
.quiz-code, .quiz-answer pre { font-family: 'Roboto Mono', monospace; font-size: .85rem; background: var(--bb-code-bg); border: 1px solid var(--bb-border); border-radius: 6px; padding: .5rem .7rem; margin: .3rem 0 .6rem; white-space: pre; overflow-x: auto; }
.quiz-options { display: flex; flex-direction: column; gap: .3rem; }
.quiz-options label { display: flex; gap: .5rem; align-items: baseline; padding: .3rem .4rem; border-radius: 6px; cursor: pointer; }
.quiz-options label:hover { background: var(--bb-light-bg); }
.quiz-in { font: inherit; padding: .35rem .5rem; border: 1px solid var(--bb-border); border-radius: 6px; background: var(--bb-surface); color: var(--bb-dark); width: min(100%, 22rem); }
.quiz-out { font-family: 'Roboto Mono', monospace; font-size: .85rem; width: min(100%, 30rem); display: block; }
.quiz-order { margin: .2rem 0; padding-left: 1.5rem; }
.quiz-order li { display: flex; align-items: center; justify-content: space-between; gap: .5rem; padding: .2rem .3rem; margin: .15rem 0; border: 1px solid var(--bb-border); border-radius: 6px; background: var(--bb-code-bg); }
.quiz-order code { font-family: 'Roboto Mono', monospace; font-size: .85rem; white-space: pre; }
.quiz-move button { padding: .1rem .45rem; margin-left: .2rem; }
.quiz-actions { display: flex; align-items: center; gap: .7rem; margin-top: .6rem; }
.quiz-q.right .quiz-result { color: var(--bb-green-deep); font-weight: 700; }
.quiz-q.wrong .quiz-result { color: var(--bb-red-ink); font-weight: 700; }
.quiz-explain { margin-top: .5rem; padding: .5rem .7rem; border-radius: 6px; background: var(--bb-light-bg); font-size: .92rem; }
.quiz-explain[hidden] { display: none; }
.quiz-answer { margin-bottom: .3rem; }
.quiz-summary { font-weight: 700; }
.lesson-nav { display: flex; justify-content: space-between; gap: 1rem; margin-top: 3rem; padding-top: 1.25rem; border-top: 1px solid var(--bb-border); }
.lesson-nav a { text-decoration: none; font-weight: 700; }

/* cells */
.cell { margin: 1.25rem 0 1.75rem; border: 1px solid var(--bb-border); border-radius: 12px; overflow: hidden; background: var(--bb-surface); box-shadow: 0 .35rem 1rem rgba(0,0,0,.05); }
.cell.task { border-color: var(--bb-green-dark); }
/* accessibility: a visible focus ring, a skip link, less motion when asked */
a:focus-visible, button:focus-visible, input:focus-visible, select:focus-visible, textarea:focus-visible, [tabindex]:focus-visible { outline: 3px solid #1a5fb4; outline-offset: 2px; }
.sr-only { position: absolute; width: 1px; height: 1px; margin: -1px; padding: 0; overflow: hidden; clip: rect(0 0 0 0); white-space: nowrap; border: 0; }
.skip { position: absolute; left: -999px; top: .5rem; z-index: 100; padding: .5rem .9rem; background: #111; color: #fff; border-radius: 6px; font-weight: 700; }
.skip:focus { left: .5rem; }
@media (prefers-reduced-motion: reduce) { *, *::before, *::after { transition-duration: .01ms !important; animation-duration: .01ms !important; scroll-behavior: auto !important; } }

/* the control that sets the text size and the theme for the page */
.view-wrap { position: relative; margin-left: auto; }
.bar .view-wrap + .bar-links { margin-left: 1.1rem; }
.view-btn { font-family: 'Roboto Mono', monospace; font-weight: 700; padding: .25rem .55rem; }
.view-panel { position: absolute; z-index: 40; right: 0; top: calc(100% + .4rem); width: 15rem; padding: .6rem .7rem; border: 1px solid var(--bb-border); border-radius: 10px; background: var(--bb-surface); box-shadow: 0 .5rem 1.5rem rgba(0,0,0,.15); font-size: .85rem; }
.view-panel[hidden] { display: none; }
.view-row { display: flex; align-items: center; gap: .5rem; margin: .25rem 0; }
.view-row button { padding: .15rem .5rem; }
.view-row .view-size { font-family: 'Roboto Mono', monospace; font-size: .78rem; min-width: 4.2em; text-align: center; }

/* dark code: the editor, the console and the panels that belong to them. The page around them stays as it is. */
.bb-dark .CodeMirror-gutters { background: var(--bb-code-bg); border-right-color: var(--bb-border); }
.bb-dark .CodeMirror-linenumber { color: #6b7784; }
.bb-dark .CodeMirror-cursor { border-left-color: #e4e8ec; }
.bb-dark .CodeMirror-selected { background: #33405a; }
.bb-dark .CodeMirror-focused .CodeMirror-selected { background: #3c4c6b; }
.bb-dark .CodeMirror-activeline-background { background: #1b1f25; }
.bb-dark .cm-keyword { color: #d29ff0; }
.bb-dark .cm-string, .bb-dark .cm-string-2 { color: #a8e06a; }
.bb-dark .cm-number { color: #f5c777; }
.bb-dark .cm-comment { color: #7d8b99; }
.bb-dark .cm-def, .bb-dark .cm-builtin { color: #7cd3ff; }
.bb-dark .cm-variable, .bb-dark .cm-variable-2, .bb-dark .cm-variable-3, .bb-dark .cm-property, .bb-dark .cm-operator, .bb-dark .cm-punctuation { color: #dbe3ea; }
.bb-dark .cm-meta { color: #9fb2bf; }
.bb-dark .CodeMirror .running-line { background: rgba(122, 176, 63, .3); }
.bb-dark .console-in { caret-color: #a8e06a; }
.bb-dark .console-in:focus, .bb-dark .console-in:focus-visible { box-shadow: inset 0 -2px 0 #a8e06a; }
.bb-dark .cell-view .telemetry { text-shadow: 0 0 3px var(--bb-view-bg), 0 0 3px var(--bb-view-bg); }
.bb-dark .share-box .share-link { background: var(--bb-code-bg); color: var(--bb-dark); }
.bb-dark li.CodeMirror-hint-active { background: #33405a; color: #fff; }
.bb-dark li.CodeMirror-hint-active .h-doc, .bb-dark .CodeMirror-hint .h-doc { color: #9fb2bf; }
.bb-dark .CodeMirror-foldmarker, .bb-dark .CodeMirror-foldgutter-open, .bb-dark .CodeMirror-foldgutter-folded { color: #a8e06a; }

/* Share: the copied link, when the browser will not let the page reach the clipboard */
.share-box { display: flex; align-items: center; gap: .5rem; padding: .4rem .6rem; border-bottom: 1px solid var(--bb-border); background: var(--bb-soft); font-size: .82rem; }
.share-box label { font-weight: 700; }
.cell-view:has(.ref-panel), .cell-body:has(.ref-docked) { min-height: 24rem; }
.cell-body:has(.ref-docked) { position: relative; }
.ref-panel.ref-docked { left: auto; width: min(22rem, 100%); box-shadow: -6px 0 14px rgba(0, 0, 0, .12); }
.ref-panel { position: absolute; inset: 0; z-index: 30; display: flex; flex-direction: column; background: var(--bb-surface); color: var(--bb-dark); font-size: .82rem; border-left: 1px solid var(--bb-border); }
.ref-top { display: flex; gap: .4rem; padding: .45rem .5rem; border-bottom: 1px solid var(--bb-border); background: var(--bb-soft); }
.ref-search { flex: 1; min-width: 0; font: inherit; padding: .3rem .45rem; border: 1px solid var(--bb-border); border-radius: 5px; background: var(--bb-surface); color: var(--bb-dark); }
.ref-groups { flex: 1; overflow-y: auto; padding: .2rem .5rem .4rem; }
.ref-group { border-bottom: 1px solid var(--bb-border); }
.ref-group > summary { cursor: pointer; font-weight: 800; padding: .45rem 0; }
.ref-item { padding: .35rem 0 .5rem; border-top: 1px dashed var(--bb-border); }
.ref-item[hidden], .ref-group[hidden], .ref-none[hidden] { display: none; }
.ref-sig { font-family: 'Roboto Mono', monospace; font-weight: 500; font-size: .8rem; overflow-wrap: anywhere; }
.ref-doc { color: var(--bb-secondary); margin: .1rem 0 .3rem; }
.ref-ex { display: flex; align-items: flex-start; gap: .4rem; }
.ref-ex pre { flex: 1; min-width: 0; margin: 0; padding: .3rem .45rem; background: var(--bb-code-bg); border-radius: 5px; font-family: 'Roboto Mono', monospace; font-size: .76rem; white-space: pre-wrap; overflow-wrap: anywhere; }
.ref-insert { flex: none; font-size: .76rem; padding: .25rem .5rem; }
.ref-none, .ref-more { margin: .4rem .5rem; color: var(--bb-secondary); }
.cell-view { position: relative; }
.cell-foot .handin[hidden] { display: none; }
.cell-foot .handed.returned { color: var(--bb-red-ink); font-weight: 700; }
.cell-head .icon[hidden] { display: none; }
.test-page .test-head { display: flex; flex-wrap: wrap; align-items: baseline; gap: .3rem 1rem; }
.test-clock { font-family: 'Roboto Mono', monospace; font-size: 1.4rem; font-weight: 500; padding: .1rem .6rem; border-radius: 8px; background: var(--bb-light-bg); }
.test-clock.soon { background: var(--bb-red-bg); color: var(--bb-red-ink); }
.test-rules { color: var(--bb-secondary); margin: .2rem 0 1rem; }
.test-task { margin: 1.5rem 0; }
.test-task h2 { font-family: 'Varela Round', sans-serif; font-weight: 400; font-size: 1.25rem; margin: 0 0 .3rem; }
.class-test { margin: 0 0 1rem; padding: .7rem 1rem; border-radius: 10px; background: var(--bb-red-bg); color: var(--bb-red-ink); font-weight: 700; }
.class-test a { color: inherit; }
.cell-feedback { padding: .5rem .75rem .6rem; border-top: 1px solid var(--bb-border); background: var(--bb-note); font-size: .85rem; }
.cell-feedback[hidden] { display: none; }
.cell-feedback.returned { box-shadow: inset 4px 0 var(--bb-red-ink); }
.fb-head { display: flex; flex-wrap: wrap; gap: .2rem .5rem; align-items: baseline; }
.fb-when { color: var(--bb-secondary); font-size: .8rem; }
.fb-tag { font-size: .75rem; font-weight: 700; color: var(--bb-red-ink); }
.fb-note { margin: .3rem 0 0; white-space: pre-wrap; }
.fb-lines { list-style: none; margin: .4rem 0 0; padding: 0; display: flex; flex-direction: column; gap: .25rem; }
.fb-lines li { display: flex; flex-wrap: wrap; gap: .2rem .45rem; align-items: baseline; }
.fb-go { font-family: 'Roboto Mono', monospace; font-size: .75rem; padding: .05rem .4rem; }
.fb-lines code { font-family: 'Roboto Mono', monospace; font-size: .76rem; background: var(--bb-chip); padding: 0 .3em; border-radius: 3px; }
.CodeMirror .feedback-line { background: rgba(253, 209, 77, .28); }
.feedback-widget { margin: .1rem 0 .3rem 1.2rem; padding: .25rem .5rem; border-left: 3px solid var(--bb-amber); background: var(--bb-note); color: var(--bb-dark); font-family: 'Nunito', system-ui, sans-serif; font-size: .8rem; white-space: pre-wrap; border-radius: 0 4px 4px 0; }
.cell-foot .handed { font-size: .8rem; color: var(--bb-secondary); }
.cell-foot .handed.late { color: var(--bb-red-ink); }
.saves-box { padding: .5rem .6rem; border-bottom: 1px solid var(--bb-border); background: var(--bb-soft); font-size: .82rem; }
.saves-row { display: flex; flex-wrap: wrap; align-items: center; gap: .4rem; }
.saves-row label { font-weight: 700; }
.saves-row .spacer { flex: 1; }
.saves-box .save-name { flex: 1 1 10rem; min-width: 8rem; font: inherit; padding: .25rem .4rem; border: 1px solid var(--bb-border); border-radius: 5px; background: var(--bb-surface); color: var(--bb-dark); }
.saves-msg { margin: .3rem 0 0; min-height: 1em; color: var(--bb-secondary); }
.saves-msg:empty { display: none; }
.saves-list { list-style: none; margin: .4rem 0 0; padding: 0; max-height: 12rem; overflow-y: auto; }
.saves-list li { display: flex; align-items: center; gap: .5rem; padding: .25rem 0; border-top: 1px solid var(--bb-border); }
.saves-list .save-title { font-weight: 700; overflow-wrap: anywhere; }
.saves-list .save-when { flex: 1; color: var(--bb-secondary); font-size: .76rem; }
.saves-list li.same .save-title::before { content: "\2022  "; color: var(--bb-green-deep); }
.saves-empty, .saves-note { margin: .4rem 0 0; color: var(--bb-secondary); }
.share-box .share-link { flex: 1; min-width: 0; font-family: 'Roboto Mono', monospace; font-size: .75rem; padding: .25rem .4rem; border: 1px solid var(--bb-border); border-radius: 5px; background: var(--bb-surface); }

/* debug mode: the line that is running, the bar that steps through it, and values on hover */
.CodeMirror .running-line { background: rgba(122, 176, 63, .22); }
.debug-bar { display: flex; align-items: center; gap: .5rem; flex-wrap: wrap; padding: .4rem .6rem; border-top: 1px solid var(--bb-border); background: var(--bb-soft); font-size: .82rem; }
.debug-bar[hidden] { display: none; }      /* display: flex above would otherwise beat the browser's rule for hidden */
.debug-bar .dbg-at { font-weight: 700; }
.debug-bar .dbg-vars { font-family: 'Roboto Mono', monospace; font-size: .78rem; color: var(--bb-secondary); overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
.var-tip { position: fixed; z-index: 3000; max-width: 32rem; padding: .25rem .45rem; border-radius: 5px; background: #111; color: #fff; font-family: 'Roboto Mono', monospace; font-size: .78rem; pointer-events: none; white-space: pre; overflow: hidden; text-overflow: ellipsis; }

/* input(): the prompt and what is typed sit on the console line itself, as they would in any Python console */
.console-ask { display: inline; }
.console-in { font: inherit; color: inherit; background: transparent; border: 0; padding: 0; outline: none; width: 2ch; caret-color: var(--bb-green-deep); }
/* a box round it would not look like a console, so the focus shows as a line under what is being typed */
.console-in:focus, .console-in:focus-visible { outline: none; box-shadow: inset 0 -2px 0 var(--bb-green-deep); }

/* the legal footer under every page */
.site-foot { max-width: 1180px; margin: 0 auto; padding: 1.2rem 1.25rem 2rem; font-size: .78rem; color: var(--bb-secondary); border-top: 1px solid var(--bb-border); }
.site-foot a { color: inherit; }
body.embed .site-foot, body.expanded .site-foot { display: none; }

/* the teacher's own tasks */
.class-tasks .module-head { background: var(--bb-note); border-color: var(--bb-note-border); }
.class-task .crumb { color: var(--bb-secondary); font-size: .9rem; }
.class-task-cell { margin-top: 1rem; }

/* locked modules */
.module.locked .module-head { opacity: .55; }
.side-module.locked .side-module-title { opacity: .5; cursor: default; }

/* the class: the bar pill, the join dialog, the banner */
.classbar { display: flex; align-items: center; gap: .4rem; }
.classbar button { font: inherit; font-weight: 700; font-size: .8rem; padding: .25rem .7rem; border-radius: 999px; border: 1px solid var(--bb-dark); background: var(--bb-surface); color: var(--bb-dark); cursor: pointer; }
.classbar button.class-join { background: var(--bb-dark); color: var(--bb-cream); }
.classbar button:hover { background: var(--bb-sage); color: var(--bb-dark); }
.class-pill { font-size: .8rem; font-weight: 700; padding: .2rem .65rem; border-radius: 999px; background: var(--bb-surface); border: 1px solid var(--bb-border); }
.join-dialog { position: fixed; inset: 0; z-index: 60; background: rgba(0,0,0,.35); display: flex; align-items: center; justify-content: center; padding: 1rem; }
.join-privacy { margin: .4rem 0 0; font-size: .8rem; }
.join-school { display: grid; gap: .5rem; margin: .7rem 0 .2rem; }
.join-school button { width: 100%; font-weight: 700; }
.join-school[hidden], .join-go[hidden] { display: none; }
.join-label { display: block; font-size: .8rem; font-weight: 700; margin: .5rem 0 .15rem; }
.join-box { background: var(--bb-surface); border-radius: 12px; padding: 1.2rem 1.4rem; max-width: 380px; width: 100%; box-shadow: 0 .75rem 2rem rgba(0,0,0,.2); }
.join-box h3 { margin: 0 0 .4rem; font-family: 'Varela Round', sans-serif; font-weight: 400; }
.join-box p { margin: 0 0 .7rem; color: var(--bb-secondary); font-size: .9rem; }
.join-box input { display: block; width: 100%; font: inherit; padding: .45rem .6rem; border: 1px solid var(--bb-border); border-radius: 6px; margin: .35rem 0; }
.join-box .join-code { font-family: 'Roboto Mono', monospace; letter-spacing: .25em; text-transform: uppercase; font-weight: 700; }
.join-actions { display: flex; gap: .5rem; margin-top: .5rem; }
.join-actions button { font: inherit; font-weight: 700; padding: .4rem 1rem; border-radius: 6px; border: 1px solid var(--bb-green-dark); background: var(--bb-surface); cursor: pointer; }
.join-actions button.primary { background: var(--bb-green); border-color: var(--bb-green); color: var(--bb-on-green); }
.join-msg { min-height: 1.2em; color: var(--bb-red); font-size: .85rem; }
.class-banner { margin: .6rem 0 1rem; display: flex; flex-direction: column; gap: .4rem; }
.class-msg, .class-hint { border-radius: 10px; padding: .55rem .9rem; font-size: .95rem; border: 1px solid var(--bb-border); background: var(--bb-light-bg); }
.class-hint { background: var(--bb-note); border-color: var(--bb-note-border); }
.class-assign { border-radius: 10px; padding: .55rem .9rem; font-size: .95rem; border: 1px solid var(--bb-border); background: var(--bb-surface); }
.class-assign.done { background: var(--bb-light-bg); }
.class-assign.late { border-color: #e0b4b1; background: #fbeeed; }
.class-assign .assign-note { color: var(--bb-secondary); margin-top: .2rem; }
.class-assign .assign-links { display: flex; flex-wrap: wrap; gap: .3rem .8rem; margin-top: .35rem; font-size: .88rem; }
.progress-pill.assigned { background: var(--bb-note); border-color: var(--bb-note-border); margin-right: .4rem; }
.lesson-card.assigned { border-color: var(--bb-note-border); }
.class-banner .tag { font-size: .72rem; font-weight: 800; letter-spacing: .06em; text-transform: uppercase; color: var(--bb-secondary); margin-right: .5rem; }

/* notifications: bubbles in the corner that follow the student across pages until dismissed */
.toasts { position: fixed; top: 3.6rem; right: 1rem; z-index: 55; display: flex; flex-direction: column; gap: .5rem; width: min(360px, calc(100vw - 2rem)); pointer-events: none; }
.toast { pointer-events: auto; display: grid; grid-template-columns: minmax(0, 1fr) auto; gap: .5rem; align-items: start; background: var(--bb-surface); border: 1px solid var(--bb-border); border-left: 5px solid var(--bb-green-dark); border-radius: 10px; padding: .55rem .5rem .6rem .85rem; box-shadow: 0 .6rem 1.6rem rgba(0,0,0,.16); font-size: .93rem; animation: toast-in .2s ease-out; }
.toast.hint { border-left-color: var(--bb-amber); background: var(--bb-note); }
.toast.asg { border-left-color: #6f8544; }
.toast .tag { display: block; font-size: .7rem; font-weight: 800; letter-spacing: .06em; text-transform: uppercase; color: var(--bb-secondary); margin-bottom: .15rem; }
.toast-text { white-space: pre-wrap; overflow-wrap: anywhere; }
.toast-link { display: inline-block; margin-top: .3rem; font-weight: 700; }
.toast-x { border: 0; background: transparent; font-size: 1rem; line-height: 1; padding: .2rem .45rem; color: var(--bb-secondary); cursor: pointer; }
.toast-x:hover { color: var(--bb-dark); background: var(--bb-light-bg); }
.toast.out { opacity: 0; transform: translateX(1rem); transition: opacity .18s, transform .18s; }
@keyframes toast-in { from { opacity: 0; transform: translateY(-.4rem); } to { opacity: 1; transform: none; } }
@media (max-width: 700px) { .toasts { top: auto; bottom: 4.6rem; right: .6rem; width: calc(100vw - 1.2rem); } }

/* the consent bar for analytics cookies */
.consent { position: fixed; left: 50%; bottom: 1rem; transform: translateX(-50%); z-index: 50; display: flex; align-items: center; gap: .6rem; max-width: calc(100% - 2rem); padding: .55rem .9rem; border-radius: 999px; background: #111; color: #fff; font-size: .85rem; box-shadow: 0 .5rem 1.5rem rgba(0,0,0,.25); }
.consent button { font: inherit; font-weight: 700; font-size: .8rem; padding: .3rem .8rem; border-radius: 999px; border: 1px solid #fff; background: transparent; color: #fff; cursor: pointer; white-space: nowrap; }
.consent button.primary { background: var(--bb-green); border-color: var(--bb-green); color: var(--bb-on-green); }
@media (max-width: 600px) { .consent { flex-wrap: wrap; border-radius: 12px; left: .6rem; right: .6rem; transform: none; max-width: none; padding: .5rem .8rem; } .consent button { min-height: 40px; } }

/* the loading bar: a stripe that sweeps under the cell head while the simulator is working */
/* the track is always there, so nothing shifts when a run starts; it only sweeps while the page is waiting for
   Python to load and start. Once the robot is moving there is nothing left to wait for. */
.cell-progress { height: 4px; background: var(--bb-light-bg); position: relative; overflow: hidden; }
.cell-progress::before { content: ""; position: absolute; top: 0; bottom: 0; left: 0; width: 0; border-radius: 2px; background: var(--bb-green-dark); }
.cell.loading .cell-progress::before { left: -40%; width: 40%; animation: cell-sweep 1.1s ease-in-out infinite; }
@keyframes cell-sweep { from { left: -40%; } to { left: 100%; } }
@media (prefers-reduced-motion: reduce) { .cell.loading .cell-progress::before { animation: none; left: 0; width: 100%; opacity: .6; } }
/* the head: the title with the buttons on its right, the task's description on its own line under it */
.cell-head { position: relative; display: grid; grid-template-columns: minmax(0, 1fr) repeat(5, auto); align-items: center; column-gap: .35rem; row-gap: .15rem; padding: .45rem .75rem; background: var(--bb-sage); border-bottom: 1px solid var(--bb-border); font-size: .85rem; }
.cell-head .label { font-weight: 700; min-width: 0; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
.cell-head .task-hint { color: var(--bb-ink-dim); grid-column: 1 / -1; grid-row: 2; min-width: 0; }
.cell-head .task-hint code { font-family: 'Roboto Mono', monospace; font-size: .92em; background: var(--bb-chip); padding: 0 .3em; border-radius: 3px; }
.cell-head .spacer { display: none; }
.cell-head .task-stdin { color: var(--bb-ink-dim); grid-column: 1 / -1; grid-row: 3; min-width: 0; }
.cell-head .task-stdin code { font-family: 'Roboto Mono', monospace; font-size: .92em; background: var(--bb-chip); padding: 0 .3em; border-radius: 3px; margin-right: .2em; }
.cell-head .task-stdin code.empty { font-style: italic; }
.cell-body { display: grid; grid-template-columns: minmax(0, 1fr) 6px 300px; }
.cell .CodeMirror { height: auto; min-height: 120px; font-family: 'Roboto Mono', monospace; font-size: var(--code-size); background: var(--bb-code-bg); color: var(--bb-dark); }
.cell .CodeMirror-scroll { min-height: 120px; max-height: 420px; }
.cell-view { position: relative; background: var(--bb-view-bg); border-left: 1px solid var(--bb-border); min-height: 220px; }
.cell-view canvas.view3d { position: absolute; inset: 0; width: 100%; height: 100%; display: block; }
/* the robot view is painted on the shared canvas, which sits above the page, so the readout lives in the
   top-left corner where the mat never reaches */
.cell-view .telemetry { position: absolute; z-index: 6; left: .5rem; top: .4rem; font-family: 'Roboto Mono', monospace; font-size: 11px; color: var(--bb-secondary); pointer-events: none; background: transparent; padding: 0; text-shadow: 0 0 3px #fff, 0 0 3px #fff; }
.cell-view .telemetry:empty { display: none; }
.cell-view .placeholder { position: absolute; inset: 0; display: flex; align-items: center; justify-content: center; color: var(--bb-secondary); font-size: .85rem; }
.cell-head .icon, .cell-head .view-btn { display: inline-flex; align-items: center; justify-content: center; padding: .34rem; line-height: 0; }
.cell-head .view-btn { font-family: 'Roboto Mono', monospace; line-height: 1; min-width: 2rem; }
/* what just happened, said next to the icons: out of the grid, so it cannot push a button onto a second row */
.cell-head .share-said { position: absolute; z-index: 6; top: 100%; right: .6rem; margin-top: 3px; padding: .15rem .5rem; border-radius: 6px; background: #111; color: #fff; font-size: .75rem; font-weight: 700; white-space: nowrap; pointer-events: none; }
.cell--full .cell-head .expand { background: var(--bb-sage); }

/* full-screen cell: the whole cell element moves into a fixed overlay; the shared canvas is raised above it */
.overlay { position: absolute; left: 0; width: 100%; height: 100vh; background: var(--bb-cream); display: flex; flex-direction: column; }
.overlay-body { flex: 1; min-height: 0; display: flex; }
.cell.cell--full { flex: 1; display: flex; flex-direction: column; margin: 0; border: 0; border-radius: 0; box-shadow: none; min-height: 0; }
.cell--full .cell-body { flex: 1; min-height: 0; grid-template-columns: minmax(0, 1fr) 6px minmax(0, 1fr); }
.cell--full .CodeMirror { height: 100%; font-size: calc(var(--code-size) + .06rem); }
.cell--full .CodeMirror-scroll { max-height: none; height: 100%; }
.cell--full .cell-view { min-height: 0; border-left: 1px solid var(--bb-border); border-top: 0; }
.cell--full .cell-view .telemetry { font-size: 14px; left: 1rem; top: .75rem; }
.cell--full .cell-lower { height: 22vh; min-height: 150px; }
/* the embed (an iframe on the main site): side by side down to phone width, a short console, no wasted height */
body.embed .cell--full .cell-body { grid-template-columns: minmax(0, 1fr) 6px minmax(0, 1fr); grid-template-rows: none; }
body.embed .cell--full .cell-lower { height: 118px; min-height: 90px; }
body.embed .cell--full .CodeMirror { font-size: calc(var(--code-size) + .03rem); }
body.embed .cell--full .cell-view { min-height: 0; }
body.embed .splitter { display: block; }     /* the 900px rule hides it, which would drop the robot view into the 6px column */
@media (max-width: 640px) { body.embed .cell--full .cell-body { grid-template-columns: 1fr !important; grid-template-rows: minmax(0, 1fr) minmax(0, 1fr); } body.embed .splitter { display: none; } .cell-foot .best { display: none; }
  /* a phone-width embed is pinned to its frame like a lesson cell: code, robot, camera and depth, console, buttons,
     all inside the height the iframe gives it. Only the code and the console scroll, so a page with the embed on
     it has one scroll bar, the page's own. */
  body.embed { height: 100dvh; overflow: hidden; }
  body.embed .embed-wrap { height: 100dvh; min-height: 0; }
  body.embed .cell.cell--full { flex: 1 1 auto; height: auto; min-height: 0; overflow: hidden; }
  body.embed .cell--full .cell-body { flex: 1 1 auto; min-height: 0; grid-template-rows: minmax(0, 1fr) minmax(0, 1fr) !important; }
  body.embed .cell--full .CodeMirror, body.embed .cell--full .CodeMirror-scroll { height: 100%; max-height: none; }
  body.embed .cell--full .cell-lower { height: auto !important; min-height: 0; flex: none; }
  body.embed .cell--full .cell-lower .cell-out { flex: none; height: 4.5rem; min-height: 0; max-height: none; overflow: auto; }
  body.embed .cell--full .cell-plot { height: 4.5rem; flex: none; }
  /* the code and the console still scroll with a finger, but without a scroll bar drawn over them */
  body.embed .CodeMirror-vscrollbar, body.embed .CodeMirror-hscrollbar, body.embed .CodeMirror-scrollbar-filler { display: none !important; }
  body.embed .cell-out { scrollbar-width: none; }
  body.embed .cell-out::-webkit-scrollbar { display: none; }
  /* the header wraps: the task title on its own line, then the buttons, so nothing runs off the edge */
  body.embed .cell--full .cell-head { display: flex; flex-wrap: wrap; align-items: center; gap: .35rem; padding: .45rem .6rem; }
  body.embed .cell--full .cell-head .label { order: 0; flex: 1 1 100%; white-space: normal; overflow: visible; }
  body.embed .cell--full .cell-head .task-hint, body.embed .cell--full .cell-head .task-stdin { order: 1; flex: 1 1 100%; }
  body.embed .cell--full .cell-head > :not(.label):not(.task-hint):not(.task-stdin) { order: 2; }
  body.embed .cell-head .embed-brand { margin-left: auto; padding-left: .25rem; }
  .cell--full .cell-view, body.embed .cell--full .cell-view { border-left: 0; border-top: 1px solid var(--bb-border); }
  .cell-view .telemetry, .cell--full .cell-view .telemetry { font-size: 9px; left: .35rem; top: .25rem; } }
/* a short frame (the tour's panel, a small iframe on someone's site): drop what can go, keep code, robot and Run */
@media (max-height: 560px) {
  body.embed .insets { display: none; }
  body.embed .cell-out { min-height: 2.6rem; max-height: 4rem; }
  body.embed .cell-lower, body.embed .cell--full .cell-lower { height: auto !important; min-height: 0; }
  body.embed .cell-foot { padding: .3rem .5rem; gap: .35rem; }
  body.embed .cell-foot .scrub, body.embed .cell-foot .best { display: none; }
}
@media (max-height: 420px) {
  body.embed .cell-out { min-height: 2rem; max-height: 2.6rem; }
  body.embed .cell-head .embed-brand { display: none; }
}

body.expanded { overflow: hidden; }
body.expanded .bar, body.expanded .side, body.expanded .drawer-toggle { visibility: hidden; }
@media (max-width: 900px) { .cell--full .cell-body { grid-template-columns: 1fr; grid-template-rows: 1fr 1fr; } .splitter { display: none; } }
.cell-foot { display: flex; align-items: center; gap: .6rem; padding: .45rem .75rem; border-top: 1px solid var(--bb-border); flex-wrap: wrap; }
button { font: inherit; font-weight: 700; font-size: .85rem; padding: .35rem .9rem; border-radius: 6px; border: 1px solid var(--bb-green-dark); background: var(--bb-surface); color: var(--bb-dark); cursor: pointer; }
button.primary { background: var(--bb-green); border-color: var(--bb-green); color: var(--bb-on-green); }
button:hover { background: var(--bb-sage); }
button:disabled { opacity: .5; cursor: default; }
.cell-foot .scrub { flex: 1; min-width: 80px; }
/* the console: always open with its own scrollbar, so running a program never resizes the robot view */
.cell-out { flex: 1; min-width: 0; min-height: 0; padding: .5rem .75rem; font-family: 'Roboto Mono', monospace; font-size: calc(var(--code-size) - .05rem); white-space: pre-wrap; background: var(--bb-code-bg); overflow: auto; }
.cell-out:empty::before { content: "console: what your program prints appears here"; color: var(--bb-placeholder); }
.cell-out .err { color: var(--bb-red); }
.cell-out .radio { color: var(--bb-secondary); margin-top: .4rem; }
.verdict { font-weight: 700; padding: .25rem .6rem; border-radius: 6px; font-size: .85rem; }
.verdict.pass { background: var(--bb-green); color: var(--bb-on-green); }
.verdict.fail { background: var(--bb-red-bg); color: var(--bb-red-ink); }
.best { font-size: .8rem; color: var(--bb-secondary); }

@media (max-width: 900px) {
  .lesson { grid-template-columns: 1fr; gap: .5rem; }
  .drawer-toggle { display: inline-block; align-self: start; margin: .25rem 0 .5rem; }
  .side { position: fixed; top: 0; left: 0; bottom: 0; align-self: stretch; height: 100dvh; overscroll-behavior: contain; width: min(320px, 85vw); max-height: none; background: var(--bb-surface); z-index: 26; padding: 1rem 1.25rem 2rem; box-shadow: .5rem 0 2rem rgba(0,0,0,.15); transform: translateX(-105%); transition: transform .18s ease; overflow: auto; }
  .side.open { transform: none; }
  .drawer-backdrop { position: fixed; inset: 0; background: rgba(0,0,0,.35); z-index: 25; }
  .drawer-backdrop.open { display: block; }
  body.drawer-open { overflow: hidden; }
  .cell-body { grid-template-columns: 1fr; }
  .cell-view { border-left: 0; border-top: 1px solid var(--bb-border); min-height: 240px; }
  /* the links, the Aa button and a student's class badge do not all fit on one line here: let the bar wrap */
  .bar { flex-wrap: wrap; gap: .3rem 1rem; }
  .bar-links { gap: .8rem; }
  .status { display: none; }
}

/* phones: the bar wraps (a bar that cannot wrap makes the browser zoom the whole page out), and a cell stacks
   editor over robot view, then camera and depth, then the console. The drag handles set inline sizes, so !important. */
.burger { display: none; font-size: 1.3rem; line-height: 1; padding: .2rem .55rem; border: 1px solid var(--bb-dark); background: var(--bb-surface); color: var(--bb-dark); }
@media (max-width: 700px) {
  .bar { flex-wrap: wrap; gap: .4rem .7rem; padding: .4rem .8rem; }
  .brand .logo { height: 30px; }
  .burger { display: inline-flex; margin-left: auto; }
  .bar-links { display: none; order: 5; width: 100%; margin-left: 0; flex-direction: column; gap: .15rem; padding: .3rem 0 .2rem; font-size: .95rem; }
  .bar-links a { padding: .35rem .2rem; border-top: 1px solid rgba(0,0,0,.08); }
  .bar.menu-open .bar-links { display: flex; }
  .classbar { margin-left: 0; }
  .status { display: none; }
  .index { padding: 1.25rem .9rem 3rem; }
  .lesson { padding: .75rem .8rem 0; }
  .main { padding-bottom: 3rem; }
  .cell-body, .cell--full .cell-body, .cell.arena .cell-body { grid-template-columns: 1fr !important; grid-template-rows: auto minmax(170px, 28vh); }
  .cell--full .cell-body { grid-template-rows: minmax(0, 1fr) minmax(0, 1fr); }
  .splitter, .hsplitter { display: none; }
  .cell-view, .cell.arena .cell-view { border-left: 0; border-top: 1px solid var(--bb-border); min-height: 0; }
  .cell .CodeMirror-scroll { max-height: 30vh; }
  .cell-lower, .cell--full .cell-lower { flex-direction: column; height: auto !important; min-height: 0; }
  /* one column on a phone: code, the robot, the camera and depth grid side by side, then the console under them.
     The console is what a program talks to you through, so it always has room of its own. */
  .cell-lower .insets { order: 1; border-left: 0; border-bottom: 1px solid var(--bb-border); border-top: 0; height: 6.5rem; flex-direction: row; justify-content: center; gap: .5rem; padding: .45rem; }
  .cell-lower .cell-out { order: 2; min-height: 4.5rem; max-height: 9rem; }
  .cell-plot { height: 5.75rem; }
  .cell-lower .cam-inset { height: 100%; width: auto; aspect-ratio: 4 / 3; }
  .cell-lower .tof-inset { height: 100%; width: auto; aspect-ratio: 1; }
  .cell-lower .inset-label { font-size: 10px; }
  /* tap targets a finger can hit (about 40px) */
  .burger { min-width: 44px; min-height: 44px; justify-content: center; align-items: center; }
  .classbar button { min-height: 40px; padding: .3rem .9rem; }
  .cell-head .icon, .cell-head .view-btn { min-width: 40px; min-height: 40px; }
  .cell-foot button { min-height: 40px; }
  .bar-links a { padding: .6rem .2rem; }
  .side a { padding: .5rem 0; }
  .side-module-title { min-height: 40px; }
  .lesson-nav a { display: inline-block; padding: .6rem 0; }
  .feedback .fb-open { min-height: 36px; }
  .cell-foot .scrub { height: 28px; }
  .cell-out { min-height: 4.5rem; max-height: 9rem; }
  .cell-head { padding: .4rem .6rem; }
  .cell-foot { gap: .45rem; padding: .4rem .6rem; }
  /* the buttons follow you down the cell, so Run is never below the fold while you are typing.
     overflow: hidden on the cell would stop sticky working, so the corners are rounded on the parts instead. */
  .cell { overflow: visible; }
  .cell .cell-head { border-radius: 11px 11px 0 0; }
  .cell .cell-foot { border-radius: 0 0 11px 11px; }
  .cell-foot { position: sticky; bottom: 0; z-index: 9; background: var(--bb-surface); box-shadow: 0 -.35rem .8rem rgba(0, 0, 0, .06); }
  .cell.task .cell-foot { border-top-color: var(--bb-green-dark); }
  body:not(.embed) .cell--full .cell-foot, body.expanded .cell-foot { position: static; box-shadow: none; }
  body.embed .cell--full .cell-foot { position: static; box-shadow: none; flex: none; }
  /* the verdict is the thing you came back for: keep it on its own line, readable */
  .cell-foot .verdict { flex-basis: 100%; order: 9; }
  .cell-foot .run { min-width: 6.5rem; }
}

/* a narrow window on a laptop is a phone as far as a cell is concerned */
@media (min-width: 701px) and (max-width: 900px) {
  .cell-body { grid-template-rows: auto minmax(180px, 30vh); }
  .cell .CodeMirror-scroll { max-height: 36vh; }
  .cell-lower { height: 118px; }
}

/* games */
/* the whole game card is the link */
.module.game .module-head { display: flex; border: 1px solid var(--bb-green-dark); border-radius: 12px; padding: 1rem 1.25rem; background: var(--bb-green); align-items: center; color: var(--bb-on-green); text-decoration: none; cursor: pointer; transition: box-shadow .15s, transform .15s; }
.module.game .module-head .num, .module.game .module-head p { color: var(--bb-on-green-dim); }
.module.game .module-head:hover, .module.game .module-head:focus-visible { box-shadow: 0 .35rem 1rem rgba(0, 0, 0, .12); transform: translateY(-1px); }
.module.game .md-button { text-decoration: none; font-weight: 700; padding: .45rem 1.1rem; border-radius: 6px; background: var(--bb-green); color: var(--bb-on-green); border: 1px solid var(--bb-green); white-space: nowrap; }
.side-game { display: block; margin: .2rem 0 .6rem; font-weight: 700; }
.cell.arena .cell-body { grid-template-columns: minmax(0, 1fr) 6px minmax(0, 1fr); }
.cell.arena .cell-view { min-height: 320px; }
.leaderboard table { width: 100%; border-collapse: collapse; font-size: .9rem; }
.leaderboard th, .leaderboard td { text-align: left; padding: .35rem .75rem; border-top: 1px solid var(--bb-border); }
.leaderboard thead th { font-size: .72rem; letter-spacing: .06em; text-transform: uppercase; color: var(--bb-secondary); border-top: 0; }
.leaderboard tr.me td { background: rgba(162, 197, 148, .25); font-weight: 700; }
.leaderboard .swatch { display: inline-block; width: 10px; height: 10px; border-radius: 3px; margin-right: .45rem; vertical-align: middle; }
@media (max-width: 900px) { .cell.arena .cell-body { grid-template-columns: 1fr; } }

/* rooms */
.room { border-top: 1px solid var(--bb-border); padding: .6rem .75rem .75rem; background: var(--bb-light-bg); }
.room-head { display: flex; align-items: center; gap: .75rem; margin-bottom: .5rem; }
.room-head .label { font-weight: 700; }
.room-status { font-size: .85rem; color: var(--bb-secondary); }
.room-status.ok { color: var(--bb-green-deep); }
.room-status.err { color: var(--bb-red); }
.room-join { display: flex; gap: .5rem; align-items: center; flex-wrap: wrap; }
.room-join input { font: inherit; padding: .35rem .6rem; border: 1px solid var(--bb-border); border-radius: 6px; width: 10rem; }
.room-join .or { color: var(--bb-secondary); font-size: .85rem; }
.room-code-big { font-family: 'Roboto Mono', monospace; font-size: 1.6rem; letter-spacing: .25em; font-weight: 700; margin: .25rem 0 .5rem; }
.room-people { display: flex; gap: .4rem; flex-wrap: wrap; align-items: center; margin-bottom: .6rem; }
.room-people .person { background: var(--bb-surface); border: 1px solid var(--bb-border); border-radius: 999px; padding: .15rem .6rem; font-size: .85rem; }
.room-people .person.me { border-color: var(--bb-green-dark); background: var(--bb-green); color: var(--bb-on-green); }
.room-people .count { font-size: .8rem; color: var(--bb-secondary); }
.room-actions { display: flex; gap: .5rem; flex-wrap: wrap; }
.room-note { font-size: .8rem; color: var(--bb-secondary); margin-top: .4rem; }
.board-title { font-weight: 700; padding: .5rem .75rem 0; }
.room-join[hidden], .room-live[hidden] { display: none; }

/* in a room the practice buttons go away: the race is the room's */
.cell.arena.in-room .cell-foot .run, .cell.arena.in-room .cell-foot .bots-only { display: none; }

/* embed: one cell fills the page (used inside iframes on the main site) */
body.embed .bar { display: none; }
body.embed .app { padding: 0; max-width: none; }
body.embed .embed-wrap { height: 100vh; display: flex; flex-direction: column; }


/* full-page cells (embed and full screen): the task title on its own line, the hint under it, Reload on the right */
.cell--full .cell-head { display: grid; grid-template-columns: minmax(0, 1fr) repeat(9, auto); align-items: center; row-gap: .15rem; padding: .6rem 1rem; }
.cell--full .cell-head .label { font-size: 1rem; }
.cell--full .cell-head .task-hint, .cell--full .cell-head .spacer { grid-column: 1 / -1; grid-row: 2; }
.cell--full .cell-head .spacer { display: none; }
body.embed .cell--full .cell-body { grid-template-columns: minmax(0, 3fr) 6px minmax(0, 2fr); }
body.embed .cell--full .CodeMirror { font-size: calc(var(--code-size) + .03rem); }


/* the drag handle between code and robot view */
.splitter { position: relative; cursor: col-resize; background: var(--bb-border); touch-action: none; }
.splitter::after { content: ""; position: absolute; top: 0; bottom: 0; left: -6px; right: -6px; }   /* a wider grab zone than the 6 px line */
.splitter:hover, .splitter.active { background: var(--bb-green-dark); }
body.splitting { user-select: none; cursor: col-resize; }
.hsplitter { position: relative; height: 6px; cursor: row-resize; background: var(--bb-border); touch-action: none; }
.hsplitter::after { content: ""; position: absolute; left: 0; right: 0; top: -5px; bottom: -5px; }
.hsplitter:hover, .hsplitter.active { background: var(--bb-green-dark); }
body.splitting-v { user-select: none; cursor: row-resize; }



/* the lower row: the console on the left, the sensor views (camera with detections, depth grid) on the right.
   The camera view is rendered on the shared canvas into its rectangle; the detections are drawn over it. */
.cell-lower { display: flex; align-items: stretch; height: 150px; border-top: 1px solid var(--bb-border); }
/* the chart: only there once a program has called plot(), and it takes the full width under the console */
.cell-plot { height: 104px; border-top: 1px solid var(--bb-border); background: var(--bb-surface); }
.cell-plot canvas { display: block; width: 100%; height: 100%; }
.insets { display: flex; gap: .4rem; padding: .4rem; flex: none; order: 2; background: var(--bb-light-bg); border-left: 1px solid var(--bb-border); }   /* on the right of the console */
.cam-inset { position: relative; height: 100%; aspect-ratio: 4 / 3; border: 1px solid var(--bb-border); border-radius: 4px; overflow: hidden; background: var(--bb-cam-bg); }
.cam-inset canvas.cam3d { position: absolute; inset: 0; width: 100%; height: 100%; display: block; }
.cam-overlay { position: absolute; inset: 0; z-index: 7; pointer-events: none; }
.inset-label { position: absolute; z-index: 8; left: 4px; top: 2px; font: 600 10px 'Nunito', sans-serif; color: #fff; text-shadow: 0 0 3px rgba(0,0,0,.8); letter-spacing: .04em; text-transform: uppercase; pointer-events: none; }
.det { position: absolute; border: 2px solid #ffe14d; border-radius: 2px; box-sizing: border-box; }
.det span { position: absolute; left: 0; top: 100%; white-space: nowrap; font: 500 10px 'Roboto Mono', monospace; color: #fff; text-shadow: 0 0 3px rgba(0,0,0,.9); }
.det.blob { border-radius: 50%; border-color: #fff; }
.det.blob.red { border-color: #ff6b6b; } .det.blob.blue { border-color: #7aa7ff; } .det.blob.green { border-color: #7fe07f; } .det.blob.yellow { border-color: #ffe14d; }
.tof-inset { position: relative; height: 100%; aspect-ratio: 1; border: 1px solid var(--bb-border); border-radius: 4px; background: #444; overflow: hidden; }
.tof-cells { position: absolute; inset: 0; display: grid; grid-template-columns: repeat(8, 1fr); grid-template-rows: repeat(8, 1fr); gap: 1px; }
.tof-cells i { display: block; background: #555; }
@media (max-width: 900px) { .cell-lower { height: 120px; } }
.det.line { border-radius: 50%; border-color: #ff8c42; }

/* glossary: a term in the prose, and the one floating tooltip */
.gloss { border-bottom: 1px dashed var(--bb-green-deep); cursor: help; outline: none; }
.gloss:hover, .gloss:focus { background: rgba(162, 197, 148, .3); border-radius: 3px; }
#glosspop { position: fixed; z-index: 40; max-width: 360px; opacity: 0; visibility: hidden; transition: opacity .12s ease; pointer-events: none; background: var(--bb-surface); color: var(--bb-dark); border: 1px solid var(--bb-green-dark); border-radius: 10px; padding: .7rem .85rem; font-size: .88rem; line-height: 1.5; box-shadow: 0 .6rem 1.6rem rgba(0,0,0,.14); }
#glosspop.show { opacity: 1; visibility: visible; pointer-events: auto; }
#glosspop .gp-term { font-weight: 800; color: var(--bb-green-deep); margin-bottom: .2rem; }
#glosspop .gp-def { margin-bottom: .4rem; }
#glosspop .gp-link { display: inline-block; font-size: .8rem; font-weight: 700; text-decoration: none; }

/* feedback cards at the end of each part of a page */
.feedback { margin: .6rem 0 1.6rem; font-size: .85rem; }
.feedback .fb-open { font-size: .78rem; font-weight: 600; padding: .25rem .7rem; border-color: var(--bb-border); color: var(--bb-secondary); background: var(--bb-light-bg); }
.feedback .fb-open:hover { background: var(--bb-sage); color: var(--bb-dark); }
.feedback .fb-form { border: 1px solid var(--bb-green-dark); border-radius: 10px; padding: .7rem .9rem; background: var(--bb-light-bg); display: flex; flex-direction: column; gap: .5rem; max-width: 560px; }
.feedback .fb-form[hidden] { display: none; }
.feedback .fb-row { display: flex; align-items: center; gap: .8rem; flex-wrap: wrap; }
.feedback .fb-q { font-weight: 700; }
.feedback label { display: inline-flex; align-items: center; gap: .3rem; }
.feedback .fb-text { font: inherit; font-size: .85rem; padding: .4rem .6rem; border: 1px solid var(--bb-border); border-radius: 6px; resize: vertical; }
.feedback .fb-note { color: var(--bb-secondary); }
.feedback .fb-thanks { color: var(--bb-green-deep); font-weight: 600; }

/* squiggles and the completion popup */
.CodeMirror-lint-mark-error { background-image: none; border-bottom: 2px wavy var(--bb-red); text-decoration: underline wavy var(--bb-red); }
.CodeMirror-lint-markers { width: 10px; }
.CodeMirror-lint-tooltip { font-family: 'Nunito', sans-serif; font-size: .85rem; border: 1px solid var(--bb-border); border-radius: 8px; background: var(--bb-surface); color: var(--bb-dark); box-shadow: 0 .35rem 1rem rgba(0,0,0,.12); }
.CodeMirror-hints { font-family: 'Roboto Mono', monospace; font-size: var(--code-size); border: 1px solid var(--bb-border); border-radius: 8px; background: var(--bb-surface); box-shadow: 0 .35rem 1rem rgba(0,0,0,.12); padding: .2rem 0; max-height: 16em; }
.CodeMirror-hint { padding: .15rem .6rem; display: flex; gap: .8rem; align-items: baseline; border-radius: 0; }
.CodeMirror-hint .h-sig { white-space: nowrap; }
.CodeMirror-hint .h-doc { font-family: 'Nunito', sans-serif; font-size: .78rem; color: var(--bb-secondary); white-space: nowrap; overflow: hidden; text-overflow: ellipsis; max-width: 34em; }
li.CodeMirror-hint-active { background: var(--bb-light-bg); color: var(--bb-dark); }
li.CodeMirror-hint-active .h-doc { color: var(--bb-dark); }

/* the fold arrows in the editor gutter */
.CodeMirror-linenumber { color: var(--bb-secondary); }
.bb-dark .CodeMirror-linenumber { color: #8a97a3; }
.CodeMirror-foldgutter { width: 1em; }
.CodeMirror-foldgutter-open, .CodeMirror-foldgutter-folded { color: var(--bb-green-deep); cursor: pointer; }
.CodeMirror-foldmarker { color: var(--bb-green-deep); text-shadow: none; font-family: inherit; }

/* wrapped lines: the continuation of a long line (usually a comment) is dimmed a little */
.CodeMirror-wrap pre.CodeMirror-line { word-break: break-word; }

/* choosing a course: GCSE, robotics or (soon) A level. The chips filter the modules below them. */
.index .level { margin: 1rem 0 1.6rem; display: flex; flex-wrap: wrap; align-items: center; gap: .5rem .75rem; }
.index .level-label { font-weight: 700; }
.index .level-chips { display: flex; flex-wrap: wrap; gap: .4rem; }
.index .level-chip { font: inherit; font-size: .85rem; font-weight: 700; padding: .35rem .85rem; border: 1px solid var(--bb-border); border-radius: 999px; background: var(--bb-surface); color: var(--bb-dark); cursor: pointer; }
.index .level-chip:hover { background: var(--bb-sage); }
.index .level-chip.on { background: var(--bb-dark); color: var(--bb-surface); border-color: var(--bb-dark); }
.index .level-chip.coming { opacity: .5; cursor: default; }
.index .level-chip.coming:hover { background: var(--bb-surface); }
.index .level-blurb { flex: 1 1 100%; margin: 0; font-size: .85rem; color: var(--bb-ink-dim); }

/* the overflow menu in a cell's header: everything that is not needed on every run */
.more-wrap { position: relative; display: inline-flex; }
.more-menu { position: absolute; right: 0; top: calc(100% + .3rem); z-index: 30; min-width: 15rem; padding: .25rem; border: 1px solid var(--bb-border); border-radius: 8px; background: var(--bb-surface); box-shadow: 0 6px 18px rgba(0, 0, 0, .14); }
.more-menu[hidden] { display: none; }
.more-menu .menu-item { display: flex; align-items: center; gap: .55rem; width: 100%; font: inherit; font-size: .85rem; text-align: left; padding: .4rem .5rem; border: 0; border-radius: 6px; background: transparent; color: var(--bb-dark); cursor: pointer; }
.more-menu .menu-item:hover, .more-menu .menu-item:focus { background: var(--bb-sage); outline: none; }
.more-menu .menu-item svg { flex: none; }

/* the hint is asked for, not given: the task is to work it out first */
.cell-head .hint-btn { font: inherit; font-size: .78rem; font-weight: 700; padding: .2rem .6rem; border: 1px solid var(--bb-border); border-radius: 999px; background: var(--bb-surface); color: var(--bb-dark); cursor: pointer; white-space: nowrap; }
.cell-head .hint-btn:hover { background: var(--bb-chip); }
.cell-head .task-hint[hidden] { display: none; }

/* Run turns into Stop while a program is running, so the same button starts and ends the run */
.cell-foot .run { display: inline-flex; align-items: center; gap: .4rem; }
.cell-foot .run.stopping { background: var(--bb-red-bg); border-color: var(--bb-red-ink); color: var(--bb-red-ink); }
.cell-foot .run svg { flex: none; }

/* once a cell has files, its editor keeps one height: swapping tabs must not move the page */
.cell.has-files:not(.cell--full) .CodeMirror { height: var(--file-editor-h); }
.cell.has-files:not(.cell--full) .CodeMirror-scroll { min-height: 0; max-height: none; height: 100%; }

/* an embed on another site: a quiet link back, in the corner of the cell's header */
.embed .cell-head .embed-brand { font-size: .75rem; color: var(--bb-ink-dim); text-decoration: none; white-space: nowrap; padding-left: .5rem; }
.embed .cell-head .embed-brand b { font-weight: 700; }
.embed .cell-head .embed-brand:hover { text-decoration: underline; }
.embed .cell-head .embed-brand span { opacity: .75; }
@media (max-width: 520px) { .embed .cell-head .embed-brand span { display: none; } }