:root {
  color-scheme: light dark;
  --bg: #ffffff;
  --surface: #f6f6f2;
  --surface-2: #ebebe4;
  --line: #e1e1d8;
  --text: #17170f;
  --muted: #6b6b5f;
  --accent: #ffd000;
  --accent-soft: #fff4c2;
  --on-accent: #17170f;
  --good: #1d8a4a;
  --half: #a86300;
  --bad: #c2362f;
  --hint: #6b5500;
  --ink: #17170f;
  --ink-blue: #2563eb;
  --ink-red: #dc2626;
  --radius: 16px;
  --font: -apple-system, BlinkMacSystemFont, "SF Pro Text", system-ui, sans-serif;
  --font-display: ui-rounded, "SF Pro Rounded", -apple-system, system-ui, sans-serif;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0f0f0c;
    --surface: #1b1b16;
    --surface-2: #27271f;
    --line: #313128;
    --text: #f4f4ec;
    --muted: #a3a395;
    --accent-soft: #3a3210;
    --good: #4ade80;
    --half: #fbbf24;
    --bad: #f87171;
    --hint: #ffe066;
    --ink: #f4f4ec;
    --ink-blue: #60a5fa;
    --ink-red: #f87171;
  }
}

* { box-sizing: border-box; }

html, body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: var(--font);
  font-size: 17px;
  line-height: 1.4;
  -webkit-text-size-adjust: 100%;
  -webkit-tap-highlight-color: transparent;
  touch-action: manipulation;
  overscroll-behavior: none;
}

[hidden] { display: none !important; }

h1, h2, h3 { font-family: var(--font-display); margin: 0; line-height: 1.15; }
h1 { font-size: 34px; font-weight: 800; letter-spacing: -0.02em; }
h2 { font-size: 22px; font-weight: 700; }
h3 { font-size: 18px; font-weight: 700; }
p { margin: 0; }

.muted { color: var(--muted); }
.small { font-size: 14px; }
.maths { font-variant-numeric: lining-nums; letter-spacing: 0.01em; white-space: nowrap; }
.eyebrow { font-size: 13px; font-weight: 700; letter-spacing: 0.08em; text-transform: uppercase; color: var(--muted); }

/* --- Buttons --- */

button { font: inherit; color: inherit; }

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  min-height: 50px;
  padding: 0 24px;
  border: 0;
  border-radius: 14px;
  font-size: 17px;
  font-weight: 650;
  cursor: pointer;
  user-select: none;
  -webkit-user-select: none;
  transition: transform 0.08s ease, background 0.15s ease;
}
.btn:active { transform: scale(0.97); }
.btn:disabled { opacity: 0.4; cursor: default; transform: none; }
.btn-primary { background: var(--accent); color: var(--on-accent); }
.btn-secondary { background: var(--surface-2); }
.btn-icon { width: 50px; padding: 0; background: transparent; }
.btn-icon.active { background: var(--surface-2); }
.btn-wide { width: 100%; }
.btn .icon { width: 22px; height: 22px; }

.icon { display: inline-flex; width: 24px; height: 24px; }
.icon svg { width: 100%; height: 100%; }

.chip {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 6px 14px;
  border-radius: 999px;
  background: var(--surface-2);
  font-size: 15px;
  font-weight: 650;
  white-space: nowrap;
}
.chip-accent { background: var(--accent); color: var(--on-accent); }
.chip .icon { width: 16px; height: 16px; }
.chips { display: flex; flex-wrap: wrap; justify-content: center; gap: 8px; }

.card { background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius); }
.row { display: flex; flex-wrap: wrap; gap: 12px; }
.row-center { justify-content: center; }

/* --- Pages (menu, results, history) --- */

.page {
  max-width: 680px;
  margin: 0 auto;
  padding: calc(28px + env(safe-area-inset-top)) 20px calc(40px + env(safe-area-inset-bottom));
  display: flex;
  flex-direction: column;
  gap: 24px;
}
.page section > h2 { margin-bottom: 12px; }

.menu-head { display: flex; align-items: center; justify-content: space-between; gap: 12px; flex-wrap: wrap; }
.stack { display: flex; flex-direction: column; gap: 14px; }

.level { padding: 20px 22px; display: flex; flex-direction: column; gap: 8px; }
.level-head { display: flex; justify-content: space-between; align-items: center; min-height: 24px; }
.level .example { font-size: 22px; margin-bottom: 8px; }
.level .row .btn { flex: 1; }
.level.locked { opacity: 0.55; }
.level.locked .icon { color: var(--muted); }

.page-head { display: flex; align-items: center; gap: 4px; margin-left: -12px; }

.results-head { text-align: center; display: flex; flex-direction: column; align-items: center; gap: 8px; }
.big-score { font-family: var(--font-display); font-size: 104px; font-weight: 800; line-height: 1; letter-spacing: -0.03em; }
.big-score .out-of { font-size: 44px; color: var(--muted); font-weight: 700; }
.time { font-size: 26px; font-weight: 650; font-variant-numeric: tabular-nums; }

.result-list { list-style: none; margin: 0; padding: 4px 0; counter-reset: q; }
.result-list li {
  counter-increment: q;
  display: grid;
  grid-template-columns: 28px minmax(0, 1fr) minmax(0, 1fr) 36px;
  gap: 12px;
  align-items: center;
  padding: 12px 18px;
  border-top: 1px solid var(--line);
}
.result-list li:first-child { border-top: 0; }
.result-list li::before { content: counter(q); color: var(--muted); font-size: 14px; }
.result-a { display: flex; flex-direction: column; overflow: hidden; }
.result-a .maths, .result-q { overflow: hidden; text-overflow: ellipsis; }
.result-m { font-weight: 800; font-size: 18px; text-align: right; }
.m-good { color: var(--good); }
.m-half { color: var(--half); }
.m-bad { color: var(--bad); }

.backup { padding: 18px 20px; display: flex; align-items: center; justify-content: space-between; gap: 16px; flex-wrap: wrap; }
.backup > div { display: flex; flex-direction: column; gap: 2px; flex: 1; min-width: 220px; }

.tiles { display: grid; grid-template-columns: repeat(3, 1fr); gap: 12px; }
.tile { padding: 16px; display: flex; flex-direction: column; gap: 4px; }
.tile strong { font-family: var(--font-display); font-size: 26px; }

.list { padding: 0 18px; }
.list-row { display: flex; align-items: center; justify-content: space-between; gap: 12px; padding: 14px 0; border-top: 1px solid var(--line); }
.list-row:first-child { border-top: 0; }
.list-row > :first-child { flex: 1; }
.list-row .perfect { color: var(--good); }

.badges { display: grid; grid-template-columns: repeat(auto-fill, minmax(150px, 1fr)); gap: 12px; }
.badge { padding: 16px; display: flex; flex-direction: column; gap: 4px; opacity: 0.45; }
.badge .icon { width: 30px; height: 30px; color: var(--muted); margin-bottom: 4px; }
.badge.earned { opacity: 1; }
.badge.earned .icon { color: var(--accent); }
.badge.earned .icon svg { fill: var(--accent); stroke: var(--on-accent); stroke-width: 1.2; }

/* --- Question screen --- */

.play {
  height: 100vh;
  height: 100dvh;
  display: grid;
  grid-template-rows: auto auto minmax(140px, 1fr) auto;
  padding-top: env(safe-area-inset-top);
}

.play-bar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  padding: 8px 16px 8px 8px;
  border-bottom: 1px solid var(--line);
}
.bar-left, .bar-right { display: flex; align-items: center; gap: 12px; }
.play-title { font-weight: 650; }
.play-score { font-weight: 650; }
.play-timer { font-variant-numeric: tabular-nums; font-weight: 700; padding: 4px 12px; border-radius: 999px; background: var(--accent); color: var(--on-accent); }

.question { text-align: center; font-size: clamp(30px, 4.6vw, 46px); font-weight: 650; padding: 14px 16px; }

.pad {
  position: relative;
  margin: 0 16px;
  border-radius: var(--radius);
  background: var(--surface);
  border: 1px solid var(--line);
  overflow: hidden;
}
.pad-canvas { position: absolute; inset: 0; width: 100%; height: 100%; touch-action: none; cursor: crosshair; }

.toolbar {
  position: absolute;
  top: 10px;
  right: 10px;
  display: flex;
  align-items: center;
  gap: 2px;
  padding: 4px;
  border-radius: 999px;
  background: var(--bg);
  border: 1px solid var(--line);
  box-shadow: 0 2px 10px rgb(0 0 0 / 0.08);
}
.tool {
  width: 42px;
  height: 42px;
  border: 0;
  border-radius: 999px;
  background: transparent;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
}
.tool .icon { width: 21px; height: 21px; }
.tool.active { background: var(--surface-2); }
.tool:disabled { opacity: 0.3; cursor: default; }
.sep { width: 1px; height: 22px; background: var(--line); margin: 0 4px; }
.swatch span { width: 20px; height: 20px; border-radius: 999px; border: 2px solid transparent; }
.swatch.active span { box-shadow: 0 0 0 2px var(--bg), 0 0 0 4px var(--text); }
.swatch-ink span { background: var(--ink); }
.swatch-blue span { background: var(--ink-blue); }
.swatch-red span { background: var(--ink-red); }

.solution { position: absolute; inset: 0; display: grid; place-items: center; padding: 16px; background: color-mix(in srgb, var(--surface) 88%, transparent); overflow: auto; }
.solution-card { background: var(--bg); border: 1px solid var(--line); border-radius: var(--radius); padding: 20px 24px; display: flex; flex-direction: column; gap: 12px; box-shadow: 0 8px 30px rgb(0 0 0 / 0.12); }
.grid { border-collapse: collapse; font-size: 22px; }
.grid th, .grid td { border: 1px solid var(--line); padding: 8px 16px; text-align: center; }
.grid th { background: var(--surface-2); font-weight: 650; }
.grid .corner { color: var(--muted); }
.working { font-size: 20px; white-space: normal; }
.answer-line { font-weight: 750; }

.answer {
  padding: 10px 16px calc(12px + env(safe-area-inset-bottom));
  display: flex;
  flex-direction: column;
  gap: 8px;
}
.preview { font-size: 22px; min-height: 30px; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
.message { min-height: 24px; font-weight: 650; }
.message:empty { display: none; }
.message-good { color: var(--good); }
.message-half { color: var(--half); }
.message-bad { color: var(--bad); }
.message-hint { color: var(--hint); }

.entry { display: flex; flex-direction: column; gap: 8px; }
.input-row { display: flex; gap: 8px; }
.answer-input {
  flex: 1;
  min-width: 0;
  height: 54px;
  padding: 0 16px;
  border-radius: 14px;
  border: 2px solid var(--line);
  background: var(--surface);
  color: var(--text);
  font: inherit;
  font-size: 24px;
}
.answer-input:focus { outline: none; border-color: var(--accent); }
.answer-input::placeholder { color: var(--muted); font-size: 18px; }

.keypad { display: grid; grid-template-columns: repeat(18, 1fr); gap: 6px; }
.key {
  height: 52px;
  border: 0;
  border-radius: 12px;
  background: var(--surface-2);
  font-size: 22px;
  font-weight: 550;
  cursor: pointer;
  user-select: none;
  -webkit-user-select: none;
  display: inline-flex;
  align-items: center;
  justify-content: center;
}
.key:active { background: var(--accent); color: var(--on-accent); }
.key-action { font-size: 16px; }
.key-power { font-size: 34px; }
.key .icon { width: 24px; height: 24px; }

@media (max-width: 1050px) {
  .keypad { grid-template-columns: repeat(9, 1fr); }
}

@media (max-width: 600px) {
  .tiles { grid-template-columns: 1fr; }
  .result-list li { grid-template-columns: 24px minmax(0, 1fr) 30px; }
  .result-list .result-q { grid-column: 2 / 4; }
  .result-list .result-a { grid-column: 2; }
  .toolbar { left: 10px; right: 10px; justify-content: space-between; overflow-x: auto; }
  .play-title { font-size: 14px; }
}

.confetti { position: fixed; inset: 0; width: 100vw; height: 100vh; pointer-events: none; z-index: 10; }