/* Rung v1.4 visual refresh: warm, friendly and calm. Atkinson Hyperlegible for reading, Fredoka for headings. */
:root {
  --bg: #FBF7F0;
  --bg-2: #F4EDE1;
  --card: #FFFFFF;
  --ink: #1E2A3A;
  --muted: #5E6878;
  --line: #E8E0D2;
  --rung: #F2A33A;
  --rung-deep: #D9861A;
  --rung-soft: #FDEFD8;
  --accent: #3563E9;
  --accent-ink: #FFFFFF;
  --accent-soft: #E7EEFF;
  --good: #1F8A5B;
  --good-soft: #E1F4EA;
  --warn: #B4540A;
  --warn-soft: #FDEEDD;
  --shadow-sm: 0 1px 2px rgba(30, 42, 58, .06);
  --shadow: 0 1px 2px rgba(30, 42, 58, .05), 0 8px 24px rgba(30, 42, 58, .07);
  --radius: 18px;
  --display: "Fredoka", "Atkinson Hyperlegible", system-ui, sans-serif;
  color-scheme: light;
}
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #15181E;
    --bg-2: #1B1F27;
    --card: #20252E;
    --ink: #EEF1F6;
    --muted: #A3ACBA;
    --line: #313846;
    --rung: #F5B04F;
    --rung-deep: #F5B04F;
    --rung-soft: #3A2E1C;
    --accent: #7C9BFF;
    --accent-ink: #0F1422;
    --accent-soft: #232C44;
    --good: #52C893;
    --good-soft: #173628;
    --warn: #F4A65E;
    --warn-soft: #3A2A1A;
    --shadow-sm: none;
    --shadow: 0 8px 24px rgba(0, 0, 0, .25);
    --mark-bg: #2C3544;
    color-scheme: dark;
  }
}

* { box-sizing: border-box; }
html, body { margin: 0; }
body {
  background:
    radial-gradient(1200px 400px at 50% -120px, var(--rung-soft), transparent 70%),
    var(--bg);
  color: var(--ink);
  font-family: "Atkinson Hyperlegible", system-ui, -apple-system, "Segoe UI", sans-serif;
  font-size: 17px;
  line-height: 1.5;
  padding-bottom: 300px; /* room for the composer and ladder */
  min-height: 100vh;
}
h1, h2 { margin: 0; line-height: 1.2; font-family: var(--display); font-weight: 600; }
h2 { font-size: 1.05rem; }
.small { font-size: .85rem; }
.muted { color: var(--muted); }
.sr-only { position: absolute; width: 1px; height: 1px; overflow: hidden; clip: rect(0 0 0 0); white-space: nowrap; }
[hidden] { display: none !important; }
svg { display: block; }

.top, .wrap, .composer-inner { max-width: 720px; margin-left: auto; margin-right: auto; }

/* Header */
.top { display: flex; align-items: center; justify-content: space-between; padding: 20px 16px 6px; }
.brand { display: flex; align-items: center; gap: 12px; }
.mark {
  width: 44px; height: 44px; border-radius: 12px; background: var(--mark-bg, #1E2A3A); display: grid; place-items: center;
  box-shadow: var(--shadow-sm);
}
.mark svg { width: 30px; height: 30px; }
.brand h1 { font-size: 1.7rem; letter-spacing: .01em; }
.tagline { margin: 0; color: var(--muted); font-size: .92rem; }
.link-btn { background: none; border: none; color: var(--accent); cursor: pointer; font: inherit; padding: 0; text-decoration: underline; text-underline-offset: 3px; }
.top .link-btn {
  text-decoration: none; font-weight: 700; font-size: .9rem; padding: 8px 14px; border-radius: 999px;
  background: var(--card); border: 1px solid var(--line); color: var(--ink); box-shadow: var(--shadow-sm);
}
.top .link-btn:hover { border-color: var(--muted); }

.wrap { padding: 10px 16px 16px; display: grid; gap: 16px; grid-template-columns: minmax(0, 1fr); }
.wrap > * { min-width: 0; }

.card {
  background: var(--card); border: 1px solid var(--line); border-radius: var(--radius);
  box-shadow: var(--shadow); padding: 20px;
}

/* Skill map: a path of five skills, each with a progress ring */
.skills-head { display: flex; justify-content: space-between; align-items: baseline; margin-bottom: 10px; }
.skill-list {
  list-style: none; margin: 0; padding: 14px 8px 12px; display: grid; grid-template-columns: repeat(5, 1fr);
  background: var(--card); border: 1px solid var(--line); border-radius: var(--radius); box-shadow: var(--shadow-sm);
  position: relative;
}
.skill { display: grid; justify-items: center; gap: 4px; text-align: center; position: relative; min-width: 0; padding: 0 4px; }
.skill + .skill::before { /* connector line between nodes */
  content: ""; position: absolute; top: 21px; right: calc(50% + 24px); width: calc(100% - 48px); height: 3px;
  background: var(--line); border-radius: 2px;
}
.skill.mastered + .skill::before { background: var(--good); }
.node {
  --pct: 0; width: 44px; height: 44px; border-radius: 50%; display: grid; place-items: center;
  background: conic-gradient(var(--rung) calc(var(--pct) * 1%), var(--line) 0);
  transition: background .5s ease;
}
.core {
  width: 34px; height: 34px; border-radius: 50%; background: var(--card); display: grid; place-items: center;
  font-family: var(--display); font-weight: 600; font-size: 1rem; color: var(--ink);
}
.core svg { width: 16px; height: 16px; }
.skill .name { font-weight: 700; font-size: .8rem; line-height: 1.2; max-width: 100%; }
.skill .short { display: none; }
.skill .state { font-size: .72rem; color: var(--muted); }
.skill.current .node { box-shadow: 0 0 0 4px var(--rung-soft); }
.skill.current .core { background: var(--rung-soft); }
.skill.mastered .node { background: var(--good); }
.skill.mastered .core { color: var(--good); }
.skill.mastered .state { color: var(--good); font-weight: 700; }
.skill.locked { opacity: .5; }
.skill.locked .core { color: var(--muted); }
@media (max-width: 560px) {
  .skill-list { padding: 12px 2px 10px; }
  .skill { padding: 0 1px; }
  .skill .full { display: none; }
  .skill .short { display: inline; }
  .skill .name { font-size: .7rem; }
  .skill .state { display: none; }
  .node { width: 38px; height: 38px; }
  .core { width: 29px; height: 29px; font-size: .9rem; }
  .skill + .skill::before { top: 18px; right: calc(50% + 21px); width: calc(100% - 42px); }
}

/* Problem card */
.problem { position: relative; overflow: hidden; padding-top: 22px; }
.problem::before { content: ""; position: absolute; inset: 0 0 auto 0; height: 5px; background: linear-gradient(90deg, var(--rung), var(--rung-deep)); }
.problem-meta { display: flex; gap: 10px; align-items: center; flex-wrap: wrap; margin-bottom: 10px; }
.pill { background: var(--rung-soft); color: var(--ink); border-radius: 999px; padding: 3px 12px; font-size: .8rem; font-weight: 700; }
.checked-note { margin-left: auto; display: inline-flex; align-items: center; gap: 5px; color: var(--good); font-weight: 700; }
.checked-note svg { width: 14px; height: 14px; }
.question { font-family: var(--display); font-weight: 500; font-size: 1.45rem; line-height: 1.35; margin: 0; }

/* Conversation */
.thread { display: grid; gap: 10px; }
.msg { max-width: 86%; padding: 11px 15px; border-radius: 16px; white-space: pre-wrap; word-wrap: break-word; box-shadow: var(--shadow-sm); }
.msg.tutor { background: var(--card); border: 1px solid var(--line); justify-self: start; border-top-left-radius: 6px; }
.msg.tutor.has-avatar { position: relative; margin-left: 44px; max-width: calc(86% - 44px); }
.avatar { position: absolute; left: -44px; top: 0; width: 34px; height: 34px; border-radius: 10px; background: var(--mark-bg, #1E2A3A); display: grid; place-items: center; border: 1px solid var(--line); }
.avatar svg { width: 22px; height: 22px; }
.msg.student { background: var(--accent); color: var(--accent-ink); justify-self: end; border-top-right-radius: 6px; font-weight: 700; }
.msg .who { display: block; font-size: .75rem; font-weight: 700; color: var(--muted); margin-bottom: 2px; }
.msg.tutor .rung-tag { color: var(--warn); }
.verdict { justify-self: start; font-size: .85rem; font-weight: 700; border-radius: 999px; padding: 4px 12px; margin-left: 44px; }
.verdict.good { background: var(--good-soft); color: var(--good); }
.verdict.bad { background: var(--warn-soft); color: var(--warn); }
.verdict.info { background: var(--rung-soft); color: var(--ink); }
.typing { display: inline-flex; gap: 4px; padding: 4px 0; }
.typing i { width: 7px; height: 7px; background: var(--muted); border-radius: 50%; animation: blink 1.2s infinite; }
.typing i:nth-child(2) { animation-delay: .2s; } .typing i:nth-child(3) { animation-delay: .4s; }
@keyframes blink { 0%, 80%, 100% { opacity: .25; } 40% { opacity: 1; } }

/* Composer: always-visible bottom bar with the hint ladder */
.composer {
  position: fixed; left: 0; right: 0; bottom: 0; padding: 0 12px calc(10px + env(safe-area-inset-bottom));
  background: linear-gradient(to top, var(--bg) 70%, transparent);
}
.composer > * { max-width: 720px; margin-left: auto; margin-right: auto; }
.composer .ladder, .composer .answer-row, .composer .row, .composer .fine { width: 100%; }
.composer::before { content: ""; display: block; height: 14px; }
.composer {
  display: flex; flex-direction: column; align-items: center;
}
.composer > .ladder {
  background: var(--card); border: 1px solid var(--line); border-radius: var(--radius) var(--radius) 0 0; border-bottom: none;
  padding: 12px 16px 10px; margin-bottom: 0; box-shadow: var(--shadow);
}
.composer > .answer-row {
  background: var(--card); border: 1px solid var(--line); border-top: 1px dashed var(--line); padding: 10px 16px 0;
}
.composer > .row.helpers, .composer > #nextRow {
  background: var(--card); border: 1px solid var(--line); border-top: none; padding: 8px 16px 12px; margin-top: 0;
  border-radius: 0 0 var(--radius) var(--radius); box-shadow: var(--shadow);
}
.composer > #nextRow { border-top: 1px dashed var(--line); padding-top: 12px; }

.ladder-head { display: flex; justify-content: space-between; align-items: baseline; margin-bottom: 7px; font-size: .85rem; }
.ladder-title { font-weight: 700; }
.ladder-status { color: var(--muted); }
.ladder.active .ladder-status { color: var(--warn); font-weight: 700; }
.rungs { list-style: none; display: grid; grid-template-columns: repeat(4, 1fr); gap: 6px; margin: 0; padding: 0; }
.rungs li { display: grid; gap: 4px; font-size: .78rem; color: var(--muted); text-align: center; }
.rungs .bar { display: block; height: 10px; border-radius: 5px; background: var(--line); transition: background .3s ease, transform .3s ease; }
.rungs li.on { color: var(--ink); font-weight: 700; }
.rungs li.on .bar { background: linear-gradient(90deg, var(--rung), var(--rung-deep)); }
.rungs li.just-lit .bar { animation: pop .6s ease; }
@keyframes pop { 0% { transform: scaleY(1); } 40% { transform: scaleY(1.8); } 100% { transform: scaleY(1); } }

.answer-row { display: flex; gap: 8px; }
.answer-row input {
  flex: 1; min-width: 0; font: inherit; font-size: 1.05rem; padding: 12px 14px; border-radius: 12px;
  border: 2px solid var(--line); background: var(--bg); color: var(--ink);
}
.answer-row input:focus { outline: none; border-color: var(--accent); background: var(--card); }
.row { display: flex; gap: 8px; margin-top: 8px; flex-wrap: wrap; }
.row.end { justify-content: flex-end; }
.btn {
  font: inherit; font-weight: 700; border-radius: 12px; padding: 10px 16px; cursor: pointer;
  border: 2px solid var(--line); background: var(--card); color: var(--ink);
  display: inline-flex; align-items: center; justify-content: center; gap: 7px;
  transition: border-color .15s ease, transform .05s ease, background .15s ease;
}
.btn:hover:not(:disabled) { border-color: var(--muted); }
.btn:active:not(:disabled) { transform: translateY(1px); }
.btn:disabled { opacity: .5; cursor: not-allowed; }
.btn.primary { background: var(--ink); border-color: var(--ink); color: var(--bg); padding-left: 20px; padding-right: 20px; }
.btn.wide { flex: 1; }
.helpers .btn { flex: 1; }
.ico { width: 18px; height: 18px; flex: none; }
.fine { margin: 8px auto 0; text-align: center; }
.fine .link-btn { font-size: inherit; }

/* About dialog */
dialog {
  max-width: 560px; width: calc(100% - 32px); border: 1px solid var(--line); border-radius: var(--radius);
  background: var(--card); color: var(--ink); padding: 24px; box-shadow: var(--shadow);
}
dialog::backdrop { background: rgba(10, 14, 20, .5); }
dialog h2 { font-size: 1.35rem; margin-bottom: 8px; }
dialog li { margin-bottom: 4px; }

.done h2 { font-size: 1.3rem; margin-bottom: 6px; }

@media (max-width: 560px) {
  body { font-size: 16px; }
  .brand h1 { font-size: 1.45rem; }
  .mark { width: 38px; height: 38px; }
  .mark svg { width: 26px; height: 26px; }
  .top .link-btn { padding: 7px 11px; font-size: .82rem; }
  .question { font-size: 1.22rem; }
  .checked-note { margin-left: 0; }
  .rungs li { font-size: .7rem; }
  .composer > .ladder, .composer > .answer-row, .composer > .row.helpers, .composer > #nextRow { padding-left: 12px; padding-right: 12px; }
  .fine { font-size: .75rem; }
}

@media (prefers-reduced-motion: reduce) { * { transition: none !important; animation: none !important; } }