/* Bitsy's notebook. Light: graph paper, ink outlines, marker colors. Dark: blueprint paper.
   Layout: sticky search bar, a hero with Bitsy at the desk, course "tracks" of sticker-numbered lesson cards; lessons read as one column with a margin index. */
:root {
  --paper: #f7f8fb;
  --grid: rgba(54, 92, 160, .085);
  --grid-bold: rgba(54, 92, 160, .14);
  --ink: #17203a;          /* outlines and text */
  --ink-soft: #4b5674;
  --card: #ffffff;
  --card-2: #eef2f8;
  --teal: #3cc8bb;         /* Bitsy */
  --teal-deep: #0f7f75;
  --amber: #f5a640;        /* antenna */
  --pink: #ff7f9b;
  --violet: #8f7cff;
  --hl: rgba(60, 200, 187, .42);   /* highlighter */
  --code-bg: #141a2e;
  --code-fg: #e9ecf5;
  --right: #1f9d5b;
  --wrong: #d64545;
  --bar: rgba(247, 248, 251, .9);
  --display: "Bricolage Grotesque", "Avenir Next", "Segoe UI", system-ui, sans-serif;
  --body: "Atkinson Hyperlegible", "Segoe UI", system-ui, -apple-system, sans-serif;
  --mono: "JetBrains Mono", ui-monospace, "SF Mono", Menlo, Consolas, monospace;
  --hand: "Caveat", "Comic Sans MS", cursive;
  --sh: 4px 4px 0 var(--ink);
  --sh-lg: 7px 7px 0 var(--ink);
}
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --paper: #13233f; --grid: rgba(160, 200, 255, .07); --grid-bold: rgba(160, 200, 255, .13);
    --ink: #e7eefc; --ink-soft: #a9b8d6; --card: #1a2d4f; --card-2: #22385f;
    --teal: #4fd8cb; --teal-deep: #4fd8cb; --hl: rgba(79, 216, 203, .32);
    --code-bg: #0b1426; --bar: rgba(19, 35, 63, .9); --right: #5fd48f; --wrong: #ff7a7a;
    --sh: 4px 4px 0 #050c1a; --sh-lg: 7px 7px 0 #050c1a; color-scheme: dark;
  }
}
:root[data-theme="dark"] {
  --paper: #13233f; --grid: rgba(160, 200, 255, .07); --grid-bold: rgba(160, 200, 255, .13);
  --ink: #e7eefc; --ink-soft: #a9b8d6; --card: #1a2d4f; --card-2: #22385f;
  --teal: #4fd8cb; --teal-deep: #4fd8cb; --hl: rgba(79, 216, 203, .32);
  --code-bg: #0b1426; --bar: rgba(19, 35, 63, .9); --right: #5fd48f; --wrong: #ff7a7a;
  --sh: 4px 4px 0 #050c1a; --sh-lg: 7px 7px 0 #050c1a; color-scheme: dark;
}

* { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; scroll-padding-top: 96px; }
body {
  margin: 0; color: var(--ink); font: 17.5px/1.62 var(--body);
  background-color: var(--paper);
  background-image:
    linear-gradient(var(--grid-bold) 1px, transparent 1px), linear-gradient(90deg, var(--grid-bold) 1px, transparent 1px),
    linear-gradient(var(--grid) 1px, transparent 1px), linear-gradient(90deg, var(--grid) 1px, transparent 1px);
  background-size: 120px 120px, 120px 120px, 24px 24px, 24px 24px;
}
a { color: inherit; }
img { max-width: 100%; display: block; }
:focus-visible { outline: 3px solid var(--amber); outline-offset: 3px; border-radius: 8px; }
.wrap { max-width: 1200px; margin: 0 auto; padding-left: max(20px, env(safe-area-inset-left, 0px)); padding-right: max(20px, env(safe-area-inset-right, 0px)); }
.skip { position: absolute; left: -999px; } .skip:focus { left: 16px; top: 16px; z-index: 50; background: var(--card); padding: 8px 12px; border: 2px solid var(--ink); }

/* ---------- top bar ---------- */
body::before { content: ""; position: fixed; inset: 0 0 auto; height: env(safe-area-inset-top, 0px); z-index: 30; background: var(--paper); }
.top { position: sticky; top: env(safe-area-inset-top, 0px); z-index: 20; background: var(--bar); backdrop-filter: blur(10px); -webkit-backdrop-filter: blur(10px); border-bottom: 2.5px solid var(--ink); }
.top .wrap { display: flex; align-items: center; gap: 18px; padding-block: 12px; }
.brand { display: flex; align-items: center; gap: 10px; text-decoration: none; font: 800 21px/1 var(--display); letter-spacing: -.02em; white-space: nowrap; }
.brand svg { width: 38px; height: 38px; flex: none; transition: transform .25s; }
.brand:hover svg { transform: rotate(-8deg); }
.brand b { font-weight: 800; background: linear-gradient(transparent 58%, var(--hl) 58% 92%, transparent 92%); padding: 0 2px; }
.search { position: relative; flex: 1; max-width: 640px; margin-left: auto; }
.search input { width: 100%; font: 16px var(--body); color: var(--ink); background: var(--card); border: 2.5px solid var(--ink); border-radius: 14px; padding: 11px 46px 11px 44px; box-shadow: var(--sh); transition: box-shadow .15s, transform .15s; }
.search input::placeholder { color: var(--ink-soft); }
.search input:focus { outline: none; transform: translate(-1px, -1px); box-shadow: 5px 5px 0 var(--teal-deep); }
.search .ico { z-index: 1; position: absolute; left: 14px; top: 50%; transform: translateY(-50%); width: 19px; height: 19px; color: var(--ink); pointer-events: none; }
.search kbd { position: absolute; right: 11px; top: 50%; transform: translateY(-50%); font: 600 12px var(--mono); color: var(--ink); background: var(--card-2); border: 1.5px solid var(--ink); border-radius: 6px; padding: 1px 7px; }
.theme-btn { flex: none; width: 44px; height: 44px; border-radius: 12px; border: 2.5px solid var(--ink); background: var(--amber); color: #17203a; cursor: pointer; display: grid; place-items: center; box-shadow: var(--sh); }
.theme-btn:active { transform: translate(2px, 2px); box-shadow: 2px 2px 0 var(--ink); }
.theme-btn svg { width: 19px; height: 19px; }
.results { position: absolute; left: 0; right: 0; top: calc(100% + 12px); background: var(--card); border: 2.5px solid var(--ink); border-radius: 16px; box-shadow: var(--sh-lg); max-height: min(70vh, 560px); overflow: auto; padding: 6px; }
.results a { display: grid; grid-template-columns: 92px 1fr; gap: 12px; align-items: center; padding: 8px; border-radius: 10px; text-decoration: none; }
.results a:hover, .results a.on { background: var(--card-2); }
.results img { border-radius: 7px; aspect-ratio: 16/9; object-fit: cover; border: 1.5px solid var(--ink); }
.results .t { font: 700 16px/1.3 var(--display); }
.results .s { color: var(--ink-soft); font-size: 14px; line-height: 1.4; display: -webkit-box; -webkit-line-clamp: 2; -webkit-box-orient: vertical; overflow: hidden; }
.results mark { background: var(--hl); color: inherit; border-radius: 3px; padding: 0 1px; }
.results .empty { padding: 18px; color: var(--ink-soft); }
.results .grp { font: 700 11px/1 var(--body); letter-spacing: .12em; text-transform: uppercase; color: var(--ink-soft); padding: 10px 10px 6px; }

/* ---------- hero ---------- */
.hero { padding-block: 64px 40px; display: grid; grid-template-columns: minmax(0, 1.25fr) minmax(0, .75fr); gap: 40px; align-items: center; }
.hero h1 { font: 800 clamp(42px, 6.6vw, 84px)/.98 var(--display); letter-spacing: -.035em; margin: 0 0 22px; text-wrap: balance; }
.mark { background: linear-gradient(transparent 60%, var(--hl) 60% 94%, transparent 94%); padding: 0 .06em; -webkit-box-decoration-break: clone; box-decoration-break: clone; }
.squig { position: relative; white-space: nowrap; }
.squig svg { position: absolute; left: 0; right: 0; bottom: -.16em; width: 100%; height: .28em; color: var(--amber); overflow: visible; }
.hero p { margin: 0; color: var(--ink-soft); font-size: 20px; max-width: 33em; }
.stats { display: flex; flex-wrap: wrap; gap: 10px; margin-top: 26px; }
.stat { font: 700 15px/1 var(--body); padding: 9px 12px; border: 2px solid var(--ink); border-radius: 10px; background: var(--card); }
.stat b { font: 800 17px/1 var(--display); font-variant-numeric: tabular-nums; margin-right: 4px; }
.desk { position: relative; justify-self: center; width: min(100%, 380px); }
.desk .bitsy-big { width: 62%; margin: 92px auto 0; animation: bob 3.2s ease-in-out infinite; }
.desk .bitsy-big svg { width: 100%; height: auto; overflow: visible; }
.desk .shadow { width: 46%; height: 16px; margin: 6px auto 0; background: rgba(23, 32, 58, .14); border-radius: 50%; }
.bubble { position: absolute; left: 0; right: 0; top: 0; background: var(--card); border: 2.5px solid var(--ink); border-radius: 18px; padding: 12px 16px; box-shadow: var(--sh); font: 600 15px/1.35 var(--mono); min-height: 74px; display: grid; align-content: center; }
.bubble::after { content: ""; position: absolute; left: 50%; bottom: -14px; width: 22px; height: 22px; background: var(--card); border-right: 2.5px solid var(--ink); border-bottom: 2.5px solid var(--ink); transform: translateX(-50%) rotate(45deg); }
.bubble .ans { color: var(--teal-deep); font-weight: 600; }
.bubble small { display: block; font: 700 11px/1 var(--body); letter-spacing: .12em; text-transform: uppercase; color: var(--ink-soft); margin-bottom: 6px; }
@keyframes bob { 50% { transform: translateY(-8px) rotate(-1.5deg); } }

/* ---------- topic chips ---------- */
.topics { display: flex; flex-wrap: wrap; gap: 10px; padding-block: 6px 34px; }
.chip { font: 700 15px/1 var(--body); padding: 10px 14px; border-radius: 999px; border: 2px solid var(--ink); background: var(--card); color: var(--ink); cursor: pointer; display: inline-flex; gap: 8px; align-items: center; text-decoration: none; box-shadow: 3px 3px 0 var(--ink); transition: transform .12s, box-shadow .12s; }
.chip:hover { transform: translate(-1px, -1px); box-shadow: 4px 4px 0 var(--ink); }
.chip[aria-pressed="true"] { background: var(--teal); color: #10233a; }
.chip .n { font: 700 12px var(--mono); background: var(--ink); color: var(--paper); border-radius: 999px; padding: 2px 7px; }
.chip.soon { color: var(--ink-soft); cursor: default; border-style: dashed; background: transparent; box-shadow: none; transform: none; }
.chip.soon .n { background: transparent; color: var(--ink-soft); font: 700 10px var(--body); letter-spacing: .1em; text-transform: uppercase; padding: 0; }

/* ---------- course tracks ---------- */
.course { padding-block: 34px 50px; }
.course-head { display: flex; flex-wrap: wrap; justify-content: space-between; align-items: end; gap: 14px 24px; margin-bottom: 26px; }
.tag { display: inline-block; font: 700 13px/1 var(--body); letter-spacing: .08em; text-transform: uppercase; background: var(--amber); color: #17203a; border: 2px solid var(--ink); padding: 6px 10px; border-radius: 8px; transform: rotate(-2deg); margin-bottom: 14px; }
.course[data-topic="cursed-javascript"] .tag { background: var(--pink); }
.course-head h2 { font: 800 clamp(30px, 4vw, 46px)/1.05 var(--display); letter-spacing: -.03em; margin: 0 0 10px; text-wrap: balance; }
.course-head p { margin: 0; color: var(--ink-soft); max-width: 44em; }
.btn { display: inline-flex; align-items: center; gap: 8px; font: 800 16px/1 var(--display); padding: 14px 18px; border-radius: 12px; background: var(--teal); color: #10233a; text-decoration: none; border: 2.5px solid var(--ink); box-shadow: var(--sh); cursor: pointer; white-space: nowrap; transition: transform .12s, box-shadow .12s; }
.btn:hover { transform: translate(-2px, -2px); box-shadow: 6px 6px 0 var(--ink); }
.btn:active { transform: translate(2px, 2px); box-shadow: 1px 1px 0 var(--ink); }
.btn.ghost { background: var(--card); color: var(--ink); }
.btn svg { width: 18px; height: 18px; }

.grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(260px, 1fr)); gap: 26px 22px; }
.card { position: relative; display: flex; flex-direction: column; background: var(--card); border: 2.5px solid var(--ink); border-radius: 16px; text-decoration: none; box-shadow: var(--sh); transition: transform .14s ease, box-shadow .14s ease; min-width: 0; }
.card:hover { transform: translate(-3px, -3px) rotate(-.4deg); box-shadow: var(--sh-lg); }
.card .thumb { aspect-ratio: 16/9; border-bottom: 2.5px solid var(--ink); border-radius: 13px 13px 0 0; overflow: hidden; background: #0e1017; }
.card .thumb img { width: 100%; height: 100%; object-fit: cover; transition: transform .3s; }
.card:hover .thumb img { transform: scale(1.04); }
.card .num { position: absolute; right: -12px; top: -14px; width: 46px; height: 46px; display: grid; place-items: center; font: 800 17px/1 var(--display); background: var(--amber); color: #17203a; border: 2.5px solid var(--ink); border-radius: 50%; transform: rotate(8deg); z-index: 2; }
.course[data-topic="cursed-javascript"] .card .num { background: var(--pink); }
.card .body { padding: 14px 16px 16px; display: flex; flex-direction: column; gap: 6px; flex: 1; }
.card h3 { font: 800 20px/1.2 var(--display); margin: 0; letter-spacing: -.015em; text-wrap: balance; }
.card p { margin: 0; color: var(--ink-soft); font-size: 15px; line-height: 1.45; }
.meta { margin-top: auto; padding-top: 10px; display: flex; flex-wrap: wrap; gap: 6px 14px; font: 700 13px/1.2 var(--body); color: var(--ink-soft); }
.pill { display: inline-flex; align-items: center; gap: 6px; }
.dot { width: 9px; height: 9px; border-radius: 50%; background: var(--right); border: 1.5px solid var(--ink); }
.dot.wait { background: var(--amber); }

.soon-box { margin-block: 20px 70px; padding: 30px; border: 2.5px dashed var(--ink); border-radius: 20px; display: grid; grid-template-columns: 1fr auto; gap: 24px; align-items: center; background: color-mix(in srgb, var(--card) 55%, transparent); }
.soon-box h2 { font: 800 32px/1.1 var(--display); letter-spacing: -.02em; margin: 0 0 8px; }
.soon-box p { margin: 0; color: var(--ink-soft); }
.soon-list { display: flex; flex-wrap: wrap; gap: 8px; margin-top: 16px; }

footer { border-top: 2.5px solid var(--ink); background: var(--card); color: var(--ink-soft); font-size: 15px; }
footer .wrap { display: flex; flex-wrap: wrap; justify-content: space-between; align-items: center; gap: 12px; padding-block: 26px calc(26px + env(safe-area-inset-bottom, 0px)); }
footer .sig { font: 700 24px/1 var(--hand); color: var(--ink); }
footer a { color: var(--ink); font-weight: 700; }

/* ---------- lesson ---------- */
.crumbs { font: 700 14px/1.4 var(--body); color: var(--ink-soft); padding-top: 28px; display: flex; flex-wrap: wrap; gap: 6px; }
.crumbs a { color: var(--ink-soft); text-decoration: none; } .crumbs a:hover { color: var(--ink); text-decoration: underline; }
.lesson { display: grid; grid-template-columns: minmax(0, 1fr) 300px; gap: 52px; padding-block: 14px 72px; }
.lesson h1 { font: 800 clamp(36px, 5vw, 60px)/1.02 var(--display); letter-spacing: -.035em; margin: 10px 0 16px; text-wrap: balance; }
.lesson .lede { font-size: 21px; color: var(--ink-soft); margin: 0 0 22px; max-width: 34em; }
.lesson .info { display: flex; flex-wrap: wrap; gap: 8px; margin-bottom: 28px; }
.lesson .info > span { font: 700 14px/1 var(--body); padding: 8px 11px; border: 2px solid var(--ink); border-radius: 9px; background: var(--card); display: inline-flex; align-items: center; gap: 6px; }
.video { position: relative; display: block; aspect-ratio: 16/9; border-radius: 18px; overflow: hidden; background: #0e1017; border: 2.5px solid var(--ink); box-shadow: var(--sh-lg); margin-bottom: 40px; }
.video img { width: 100%; height: 100%; object-fit: cover; }
.video iframe { position: absolute; inset: 0; width: 100%; height: 100%; border: 0; }
.video .play { position: absolute; right: 16px; top: 16px; }
.video .play > span { display: inline-flex; align-items: center; gap: 10px; background: var(--amber); color: #17203a; font: 800 16px/1 var(--display); padding: 12px 16px; border-radius: 12px; border: 2.5px solid #17203a; box-shadow: 3px 3px 0 #17203a; }
.video .play svg { width: 18px; height: 18px; }
.video:hover .play > span { transform: translate(-1px, -1px); box-shadow: 4px 4px 0 #17203a; }
article { max-width: 68ch; }
article h2 { font: 800 30px/1.15 var(--display); letter-spacing: -.02em; margin: 48px 0 12px; text-wrap: balance; }
article p { margin: 0 0 16px; }
article ul { margin: 0 0 16px; padding-left: 22px; }
article li { margin-bottom: 6px; }
article li::marker { color: var(--teal-deep); }
article code { font: 600 .86em var(--mono); background: var(--card-2); border: 1.5px solid color-mix(in srgb, var(--ink) 25%, transparent); border-radius: 6px; padding: 1px 5px; }
article strong { background: linear-gradient(transparent 62%, var(--hl) 62%); }
.box { border-radius: 16px; padding: 20px 22px; margin: 0 0 20px; border: 2.5px solid var(--ink); background: var(--card); box-shadow: var(--sh); }
.box .lbl { font: 700 13px/1 var(--body); letter-spacing: .12em; text-transform: uppercase; margin-bottom: 12px; display: flex; align-items: center; gap: 10px; }
.box .lbl svg { width: 30px; height: 30px; }
.box p:last-child { margin-bottom: 0; }
.box.eli5 { background: color-mix(in srgb, var(--teal) 16%, var(--card)); font-size: 19px; }
.box.rule { background: var(--amber); color: #17203a; transform: rotate(-.6deg); }
.box.rule p { font: 800 24px/1.3 var(--display); letter-spacing: -.01em; }
.box.rule code { background: rgba(255,255,255,.45); border-color: rgba(23,32,58,.35); color: #17203a; }
.box.mistake { border-style: dashed; box-shadow: none; }
.box.mistake .lbl { color: var(--wrong); }
pre.code { position: relative; background: var(--code-bg); color: var(--code-fg); border: 2.5px solid var(--ink); border-radius: 14px; box-shadow: var(--sh); padding: 40px 18px 16px; margin: 0 0 22px; overflow-x: auto; font: 15px/1.65 var(--mono); }
pre.code::before { content: ""; position: absolute; left: 14px; top: 13px; width: 10px; height: 10px; border-radius: 50%; background: #ff7f9b; box-shadow: 16px 0 0 #f5a640, 32px 0 0 #3cc8bb; }
pre.code code { background: none; border: 0; padding: 0; font: inherit; color: inherit; white-space: pre; }
pre.code .copy { position: absolute; right: 8px; top: 7px; font: 700 12px var(--body); color: #c9d1e6; background: #222b45; border: 1.5px solid #3a4566; border-radius: 7px; padding: 4px 9px; cursor: pointer; }
pre.code .copy:hover { color: #fff; }
.k { color: #ffb86b; } .s { color: #a6e3a1; } .n { color: #ff9e7a; } .c { color: #7f8bab; font-style: italic; } .o { color: #c3a6ff; } .p { color: #4fd8cb; }
.quiz { margin-top: 48px; }
.quiz h2 { margin-top: 0; }
.quiz .q { font: 700 19px/1.4 var(--body); margin-bottom: 14px; }
.quiz .opts { display: grid; gap: 10px; margin-bottom: 12px; }
.quiz button.opt { text-align: left; font: 16px/1.4 var(--body); color: var(--ink); background: var(--card-2); border: 2px solid var(--ink); border-radius: 12px; padding: 12px 14px; cursor: pointer; transition: transform .12s, box-shadow .12s; }
.quiz button.opt:hover:not(:disabled) { transform: translate(-1px, -1px); box-shadow: 3px 3px 0 var(--ink); }
.quiz button.opt.right { background: color-mix(in srgb, var(--right) 22%, var(--card)); border-color: var(--right); }
.quiz button.opt.wrong { background: color-mix(in srgb, var(--wrong) 16%, var(--card)); border-color: var(--wrong); }
.quiz button.opt:disabled { cursor: default; }
.quiz .why { margin-top: 6px; }
.nextprev { display: grid; grid-template-columns: 1fr 1fr; gap: 16px; margin-top: 52px; }
.nextprev a { border: 2.5px solid var(--ink); border-radius: 14px; padding: 14px 18px; text-decoration: none; background: var(--card); box-shadow: var(--sh); min-width: 0; transition: transform .12s, box-shadow .12s; }
.nextprev a:hover { transform: translate(-2px, -2px); box-shadow: var(--sh-lg); }
.nextprev small { display: block; color: var(--ink-soft); font: 700 13px/1 var(--body); margin-bottom: 6px; text-transform: uppercase; letter-spacing: .08em; }
.nextprev b { font: 800 19px/1.25 var(--display); }
.nextprev .nx { text-align: right; grid-column: 2; background: var(--teal); color: #10233a; }
.nextprev .nx small { color: #10233a; opacity: .75; }
aside.side { position: sticky; top: 96px; align-self: start; display: grid; gap: 22px; }
.side .box { padding: 18px; }
.side .box h3 { font: 700 12px/1.3 var(--body); letter-spacing: .12em; text-transform: uppercase; color: var(--ink-soft); margin: 0 0 12px; }
.side ol { list-style: none; margin: 0; padding: 0; display: grid; gap: 2px; max-height: 52vh; overflow: auto; }
.side ol a { display: grid; grid-template-columns: 28px 1fr; gap: 6px; padding: 6px 8px; border-radius: 9px; text-decoration: none; font-size: 14.5px; line-height: 1.35; color: var(--ink-soft); }
.side ol a:hover { background: var(--card-2); color: var(--ink); }
.side ol a[aria-current="page"] { background: var(--teal); color: #10233a; font-weight: 700; }
.side ol .i { font: 600 12px/1.6 var(--mono); }
.toc a { display: block; color: var(--ink-soft); text-decoration: none; padding: 4px 0; font-size: 15px; } .toc a:hover { color: var(--ink); text-decoration: underline; }

@media (max-width: 920px) {
  .lesson { grid-template-columns: minmax(0, 1fr); gap: 0; }
  aside.side { position: static; margin-top: 44px; }
  .hero { grid-template-columns: 1fr; padding-top: 36px; }
  .desk { max-width: 340px; }
}
@media (max-width: 620px) {
  body { font-size: 17px; }
  .top .wrap { flex-wrap: wrap; gap: 10px; }
  .search { order: 3; flex-basis: 100%; max-width: none; }
  .search kbd { display: none; }
  .theme-btn { margin-left: auto; width: 40px; height: 40px; }
  .soon-box { grid-template-columns: 1fr; padding: 22px; }
  .nextprev { grid-template-columns: 1fr; } .nextprev .nx { grid-column: 1; }
  .results a { grid-template-columns: 72px 1fr; }
  .card .num { right: -6px; }
  .hero p { font-size: 18px; }
  .desk { display: none; }
}
@media (prefers-reduced-motion: reduce) { *, *::before { transition: none !important; animation: none !important; } }