/* Steply website. Light, friendly, notebook colours: ink blue (the pen), highlighter yellow, paper cream. */
:root {
  --ink: #1f3a8a; --ink-2: #2f4fb0; --hl: #f4c430; --hl-soft: #fff2b8;
  --bg: #f6f3ea; --card: #ffffff; --paper: #fbf7ec; --text: #1d2433; --muted: #5d6578; --line: #e3ddcc;
  --radius: 14px;
}
* { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; }
body { margin: 0; background: var(--bg); color: var(--text); font: 16px/1.5 Inter, system-ui, sans-serif; overflow-x: hidden; }
button, input, select { font: inherit; color: inherit; }
.sr { position: absolute; width: 1px; height: 1px; overflow: hidden; clip: rect(0 0 0 0); }
[hidden] { display: none !important; }

/* ---------- top bar ---------- */
.top { display: flex; align-items: center; gap: 18px; padding: 12px 24px; background: var(--card); border-bottom: 1px solid var(--line);
       position: sticky; top: 0; z-index: 5; }
.brand { display: flex; align-items: center; gap: 8px; text-decoration: none; color: var(--ink); }
.logo { width: 30px; height: 30px; fill: var(--ink); }
.logo rect:last-child { fill: var(--hl); }
.word { font: 700 32px/1 Caveat, cursive; letter-spacing: .5px; }
.subjects { display: flex; gap: 4px; }
.subjects a { padding: 6px 12px; border-radius: 999px; text-decoration: none; color: var(--muted); font-weight: 600; font-size: 15px; }
.subjects a.on { background: var(--hl-soft); color: var(--ink); }
.lang { margin-left: auto; }
.lang select { border: 1px solid var(--line); border-radius: 10px; padding: 7px 10px; background: var(--card); font-size: 15px; }

main { max-width: 1140px; margin: 0 auto; padding: 0 20px; }

/* ---------- hero: the problem box ---------- */
.hero { text-align: center; padding: 34px 0 20px; }
h1 { margin: 0 0 20px; font-size: 32px; line-height: 1.2; font-weight: 800; letter-spacing: -.5px; }
h1 .pen { font: 700 40px/1.1 Caveat, cursive; color: var(--ink); letter-spacing: 0; }
.ask { display: flex; gap: 10px; max-width: 640px; margin: 0 auto; }
#eq { flex: 1; min-width: 0; padding: 14px 16px; font-size: 20px; border: 2px solid var(--line); border-radius: var(--radius);
      background: var(--card); outline: none; transition: border-color .15s; }
#eq:focus { border-color: var(--ink-2); }
#playBtn { padding: 0 26px; border: 0; border-radius: var(--radius); background: var(--ink); color: #fff; font-weight: 800; font-size: 18px; cursor: pointer; }
#playBtn:hover { background: var(--ink-2); }
#status { max-width: 640px; margin: 12px auto 0; color: var(--text); font-weight: 600; }
#status:empty { display: none; }
#status:not(:empty) + .examples { display: none; }   /* the note brings its own examples */
#status { background: var(--hl-soft); border-radius: 12px; padding: 10px 14px; }
.examples { display: flex; flex-wrap: wrap; gap: 8px; justify-content: center; margin-top: 14px; }

.chip, button.try { border: 1px solid var(--line); background: var(--card); border-radius: 999px; padding: 5px 12px; font-size: 15px;
        cursor: pointer; max-width: 100%; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
.chip:hover, button.try:hover { border-color: var(--ink-2); color: var(--ink); background: #f3f6ff; }
button.try { margin: 6px 4px 0; font-weight: 400; }

/* ---------- player ---------- */
.player { margin: 8px 0 30px; scroll-margin-top: 70px; }
.topics, #status { scroll-margin-top: 70px; }
.stage { display: flex; justify-content: center; }
.stage canvas { display: block; width: 100%; height: auto; border-radius: var(--radius); background: var(--paper);
                box-shadow: 0 10px 30px rgba(40, 35, 20, .16), 0 1px 3px rgba(0, 0, 0, .08); }
.stage:fullscreen { background: #111; align-items: center; }
.stage:fullscreen canvas { max-width: none !important; width: min(100vw, calc(100vh * var(--ar, 1.7778))); border-radius: 0; }
.controls { display: flex; flex-wrap: wrap; gap: 8px 14px; justify-content: center; align-items: center; margin-top: 14px; }
.ghost { border: 1px solid var(--line); background: var(--card); border-radius: 10px; padding: 7px 14px; cursor: pointer; font-weight: 600; font-size: 15px; }
.ghost:hover { border-color: var(--ink-2); }
.tog { display: flex; align-items: center; gap: 6px; color: var(--muted); font-size: 15px; }
.tog input { width: 18px; height: 18px; accent-color: var(--ink); }
.tog select { border: 1px solid var(--line); border-radius: 8px; padding: 5px 6px; background: var(--card); }

/* ---------- topic menu ---------- */
.topics { background: var(--card); border: 1px solid var(--line); border-radius: 18px; padding: 22px 24px 26px; margin-bottom: 30px; }
.topics-head { display: flex; flex-wrap: wrap; gap: 12px; align-items: center; justify-content: space-between; }
h2 { margin: 0; font-size: 24px; }
#findTopic { flex: 0 1 320px; min-width: 0; padding: 9px 14px; border: 1px solid var(--line); border-radius: 10px; background: var(--bg); }
.areas { display: flex; flex-wrap: wrap; gap: 8px; margin: 16px 0 6px; }
.areas button { border: 1px solid var(--line); background: var(--bg); border-radius: 12px; padding: 8px 14px; cursor: pointer; font-size: 15px; }
.areas button b { color: var(--ink); margin-right: 3px; }
.areas button.on { background: var(--ink); color: #fff; border-color: var(--ink); }
.areas button.on b { color: var(--hl); }
.lessons { display: grid; grid-template-columns: repeat(auto-fill, minmax(320px, 1fr)); gap: 0 26px; }
.lessons h3 { grid-column: 1 / -1; margin: 18px 0 2px; font-size: 15px; text-transform: uppercase; letter-spacing: .8px; color: var(--ink); }
.lesson { padding: 12px 0; border-bottom: 1px solid var(--line); min-width: 0; }
.lt { font-weight: 600; margin-bottom: 6px; }
.chips { display: flex; flex-wrap: wrap; gap: 6px; }
.chips .chip { font-size: 14px; padding: 3px 10px; }
.none { color: var(--muted); grid-column: 1 / -1; }

.foot { text-align: center; color: var(--muted); padding: 10px 20px 40px; }
.foot a { color: var(--ink); }
.foot .small { font-size: 14px; }

/* ---------- phones ---------- */
@media (max-width: 640px) {
  .top { padding: 10px 16px; gap: 10px; }
  .word { font-size: 28px; }
  .subjects a { padding: 5px 10px; }
  main { padding: 0 16px; }
  .hero { padding: 22px 0 14px; }
  h1 { font-size: 23px; margin-bottom: 14px; }
  h1 .pen { font-size: 31px; }
  .ask { gap: 8px; }
  #eq { font-size: 18px; padding: 12px 14px; }
  #playBtn { padding: 0 18px; font-size: 17px; }
  .examples .chip:nth-child(n+5) { display: none; }   /* four examples are enough on a phone */
  .examples { gap: 6px; }
  .chip { font-size: 14px; }
  .stage canvas { border-radius: 10px; }
  .controls { gap: 8px 10px; }
  .topics { padding: 16px; border-radius: 14px; }
  #findTopic { flex-basis: 100%; }
  .areas button { padding: 6px 10px; font-size: 14px; }
  .lessons { grid-template-columns: minmax(0, 1fr); }
}