/* app/styles/app.css — Math Driller student UI. Light theme, no framework.
   Indigo accent, teal secondary, 12px cards, 44px touch targets for iPads. */

:root {
  --ink:        #111827;
  --ink-soft:   #4b5563;
  --ink-faint:  #6b7280;
  --line:       #e5e7eb;
  --line-soft:  #f1f2f6;
  --paper:      #ffffff;
  --bg:         #f6f7fb;

  --accent:     #4f46e5;
  --accent-dk:  #4338ca;
  --accent-bg:  #eef2ff;
  --teal:       #0d9488;
  --teal-bg:    #f0fdfa;

  --ok:         #16a34a;
  --warn:       #d97706;
  --bad:        #dc2626;

  --radius:     12px;
  --shadow:     0 1px 2px rgba(17, 24, 39, .05), 0 4px 16px rgba(17, 24, 39, .06);
  --tap:        44px;
  --font: system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  font: 16px/1.5 var(--font);
  color: var(--ink);
  background: var(--bg);
  -webkit-text-size-adjust: 100%;
}

h1, h2, h3 { margin: 0; font-weight: 650; line-height: 1.25; }
p { margin: 0; }
.wrap { width: 100%; max-width: 860px; margin: 0 auto; padding: 0 16px; }
.muted { color: var(--ink-faint); }
[hidden] { display: none !important; }
:focus-visible { outline: 3px solid var(--accent); outline-offset: 2px; border-radius: 6px; }

/* --------------------------------------------------------------- chrome */

.app-header { background: var(--paper); border-bottom: 1px solid var(--line); }
.header-inner {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 8px 16px;
  padding: 14px 0;
}
.brand-title { font-size: 1.3rem; letter-spacing: -.01em; }
.brand-sub { font-size: .85rem; color: var(--ink-faint); }
.teacher-link {
  padding: 10px 12px;
  border-radius: 8px;
  background: var(--teal-bg);
  color: var(--teal);
  font-size: .9rem;
  font-weight: 600;
  text-decoration: none;
}
.teacher-link:hover { text-decoration: underline; }

#main { padding-top: 20px; padding-bottom: 88px; }
.app-footer { padding: 18px 0 28px; font-size: .8rem; color: var(--ink-faint); text-align: center; }

/* ---------------------------------------------------------------- cards */

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

.badge, .chip {
  display: inline-block;
  border-radius: 999px;
  font-weight: 650;
  white-space: nowrap;
}
.badge { padding: 2px 8px; background: var(--accent-bg); color: var(--accent-dk); font-size: .74rem; }
.chip {
  padding: 4px 10px;
  background: var(--line-soft);
  color: var(--ink-soft);
  font-size: .8rem;
  font-variant-numeric: tabular-nums;
}
.chip-score { background: var(--teal-bg); color: #0f766e; }
.chip-streak.is-hot { background: #fff7ed; color: var(--warn); }

/* -------------------------------------------------------------- buttons */

.btn {
  min-height: var(--tap);
  padding: 10px 18px;
  border: 1px solid transparent;
  border-radius: 10px;
  font: inherit;
  font-weight: 650;
  cursor: pointer;
  background: var(--line-soft);
  color: var(--ink);
}
.btn:hover { filter: brightness(.97); }
.btn:disabled { opacity: .55; cursor: default; }
.btn-primary { background: var(--accent); color: #fff; }
.btn-primary:hover { background: var(--accent-dk); filter: none; }
.btn-start { background: var(--accent-bg); color: var(--accent-dk); white-space: nowrap; }
.btn-start:hover { background: var(--accent); color: #fff; }

.linkish {
  min-height: var(--tap);
  padding: 8px 4px;
  border: 0;
  background: none;
  font: inherit;
  font-weight: 600;
  color: var(--accent);
  cursor: pointer;
}
.linkish:hover { text-decoration: underline; }
.linkish.subtle { color: var(--ink-faint); font-weight: 500; font-size: .9rem; }

/* --------------------------------------------------------- skill picker */

.picker-intro { margin-bottom: 16px; }
.picker-intro h2 { font-size: 1.15rem; margin-bottom: 4px; }
.picker-intro .muted { font-size: .9rem; max-width: 60ch; }

.level-tabs { display: flex; gap: 6px; margin-bottom: 16px; overflow-x: auto; padding-bottom: 2px; }
.level-tab {
  min-height: var(--tap);
  padding: 8px 18px;
  border: 1px solid var(--line);
  border-radius: 999px;
  background: var(--paper);
  font: inherit;
  font-weight: 600;
  color: var(--ink-soft);
  cursor: pointer;
  white-space: nowrap;
}
.level-tab.is-on { background: var(--accent); border-color: var(--accent); color: #fff; }
.level-tab.is-empty { opacity: .45; cursor: not-allowed; }

.topic-card { margin-bottom: 14px; overflow: hidden; }
.topic-head {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 10px;
  padding: 14px 16px;
  border-bottom: 1px solid var(--line);
  background: linear-gradient(180deg, #fbfbfe, var(--paper));
}
.topic-title { font-size: 1rem; }
.skill-list { display: flex; flex-direction: column; }

.skill-row {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 8px 14px;
  padding: 12px 16px;
  border-top: 1px solid var(--line-soft);
  cursor: pointer;
}
.skill-row:first-child { border-top: 0; }
.skill-row:hover { background: #fafaff; }
.skill-row.is-last { background: var(--accent-bg); }
.skill-main { display: flex; align-items: baseline; flex-wrap: wrap; gap: 8px; flex: 1 1 16ch; }
.skill-title { font-weight: 600; }
.skill-tags { font-size: .78rem; color: var(--ink-faint); }
.tag { font-size: .68rem; font-weight: 700; text-transform: uppercase; letter-spacing: .04em; color: var(--accent-dk); }
.skill-controls { display: flex; align-items: center; gap: 10px; flex-wrap: wrap; }

.tier-seg { display: inline-flex; border: 1px solid var(--line); border-radius: 10px; overflow: hidden; }
.seg {
  min-width: var(--tap);
  min-height: var(--tap);
  padding: 6px 10px;
  border: 0;
  border-left: 1px solid var(--line);
  background: var(--paper);
  font: inherit;
  font-size: .9rem;
  font-weight: 600;
  color: var(--ink-soft);
  cursor: pointer;
}
.seg:first-child { border-left: 0; }
.seg:hover { background: var(--line-soft); }
.seg.is-on { background: var(--teal); color: #fff; }

.empty-note { color: var(--ink-faint); padding: 20px 4px; }

/* ---------------------------------------------------------------- drill */

.drill-bar { display: flex; align-items: center; justify-content: space-between; gap: 10px; margin-bottom: 6px; }
.session-stats { display: flex; gap: 6px; }

.drill-head { margin-bottom: 12px; }
.drill-skill { font-size: 1.15rem; }
.drill-meta {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 8px;
  margin-top: 4px;
  font-size: .85rem;
  color: var(--ink-soft);
}
.drill-meta .muted { font-size: .8rem; }

.question-card { padding: 18px 16px 16px; }
.q-head { margin-bottom: 8px; }
.q-num { font-size: .78rem; font-weight: 700; letter-spacing: .05em; text-transform: uppercase; color: var(--accent); }
.stem { font-size: 1.12rem; line-height: 1.7; }
.note { margin-top: 6px; font-size: .86rem; color: var(--ink-faint); }

.answer-slot { margin: 16px 0 14px; }
.actions { display: flex; align-items: center; gap: 12px; flex-wrap: wrap; }

/* --------------------------------------------------------- answer input */

.ai-row { display: flex; align-items: center; gap: 8px; flex-wrap: wrap; }
.ai-row-wrap { row-gap: 10px; }
.ai-slot { display: inline-flex; align-items: center; gap: 6px; }
.ai-join { color: var(--ink-faint); font-size: .9rem; padding: 0 2px; }
.ai-affix { font-size: 1.2rem; color: var(--ink); white-space: nowrap; }
.ai-suffix { color: var(--ink-soft); }

math-field {
  font-size: 1.4rem;
  min-width: 10ch;
  min-height: var(--tap);
  padding: 6px 10px;
  border: 2px solid var(--line);
  border-radius: 10px;
  background: var(--paper);
  --caret-color: var(--accent);
  --selection-background-color: #dbeafe;
  --primary: var(--accent);
}
math-field:focus,
math-field:focus-within {
  border-color: var(--accent);
  outline: 3px solid rgba(79, 70, 229, .22);
  outline-offset: 0;
}
math-field[read-only] { background: #fafafa; border-style: dashed; }
.ai.none-active math-field { opacity: .45; }
.ai.is-locked { cursor: default; }
.ai.is-locked math-field:focus,
.ai.is-locked math-field:focus-within { outline-color: rgba(107, 114, 128, .25); border-color: var(--line); }

.ai-chips { display: flex; flex-wrap: wrap; gap: 6px; margin-bottom: 10px; }
.chip-btn {
  min-height: var(--tap);
  padding: 4px 12px;
  border: 1px solid var(--line);
  border-radius: 999px;
  background: var(--paper);
  font: inherit;
  font-size: .95rem;
  color: var(--ink-soft);
  cursor: pointer;
}
.chip-btn:hover { border-color: var(--accent); color: var(--accent-dk); }
.chip-btn:disabled { opacity: .5; cursor: default; }
.chip-none { font-weight: 650; border-style: dashed; color: var(--teal); border-color: #99f6e4; }
.chip-none.is-active { background: var(--teal); border-color: var(--teal); color: #fff; }

/* Keycap labels inside MathLive's virtual keyboard (light DOM). */
.mdk-mixed sup, .mdk-exp10 sup { font-size: .7em; }
.mdk-mixed sub { font-size: .7em; }

/* ------------------------------------------------------------- feedback */

.feedback {
  margin-top: 14px;
  padding: 12px 14px;
  border-radius: 10px;
  border: 1px solid var(--line);
  background: var(--line-soft);
}
.fb-banner { display: flex; align-items: center; gap: 8px; flex-wrap: wrap; }
.fb-icon {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  flex: 0 0 auto;
  width: 24px;
  height: 24px;
  border-radius: 999px;
  background: var(--ink-faint);
  color: #fff;
  font-size: .85rem;
  font-weight: 700;
  line-height: 1;
}
.fb-title { font-weight: 700; }
.fb-msg { margin-top: 6px; font-size: .92rem; color: var(--ink-soft); }

.fb-correct    { background: #f0fdf4; border-color: #bbf7d0; }
.fb-correct .fb-icon  { background: var(--ok); }
.fb-correct .fb-title { color: var(--ok); }
.fb-almost     { background: #fffbeb; border-color: #fde68a; }
.fb-almost .fb-icon   { background: var(--warn); }
.fb-almost .fb-title  { color: var(--warn); }
.fb-wrong      { background: #fef2f2; border-color: #fecaca; }
.fb-wrong .fb-icon    { background: var(--bad); }
.fb-wrong .fb-title   { color: var(--bad); }
.fb-incomplete { background: var(--line-soft); border-color: var(--line); }
.fb-incomplete .fb-title { color: var(--ink-faint); }

.fb-answer {
  display: flex;
  align-items: center;
  flex-wrap: wrap;
  gap: 6px;
  margin-top: 10px;
  font-size: .92rem;
  color: var(--ink-soft);
}
.fb-answer-label { font-weight: 600; }
.fb-answer-math { font-size: 1.2rem; color: var(--ink); }

.fb-working { margin-top: 10px; }
/* padding, not min-height: `display:flex` here would eat the disclosure marker */
.fb-working > summary {
  padding: 11px 0;
  cursor: pointer;
  font-size: .9rem;
  font-weight: 600;
  color: var(--accent);
}
.fb-working-body { margin-top: 6px; }
.sol-line {
  padding: 4px 0 4px 12px;
  border-left: 3px solid var(--line);
  font-size: 1.02rem;
  color: var(--ink-soft);
}
.sol-line:first-child { border-left-color: var(--accent); }

/* ------------------------------------------------------------ narrow UI */

@media (max-width: 560px) {
  .header-inner { padding-top: 10px; padding-bottom: 10px; }
  .brand-title { font-size: 1.15rem; }
  .teacher-link { font-size: .82rem; padding: 8px 10px; }
  .skill-row { align-items: stretch; }
  .skill-controls { width: 100%; justify-content: space-between; }
  .btn-start { flex: 1 1 auto; }
  .question-card { padding: 14px 12px; }
  .stem { font-size: 1.05rem; }
  .actions .btn { flex: 1 1 auto; }
}

@media (prefers-reduced-motion: no-preference) {
  .feedback { animation: fb-in .16s ease-out; }
  @keyframes fb-in { from { opacity: 0; transform: translateY(-3px); } to { opacity: 1; transform: none; } }
}