/* ============================================================
   Sudoku — Warm, elegant theme — iPad full-screen first
   ============================================================ */

:root {
  --bg: #faf7f2;
  --card: #ffffff;
  --text: #3d3229;
  --text-light: #8a7d72;
  --accent: #c9956b;
  --accent-light: #f5e6d3;
  --selected: #e8d5c0;
  --highlight: #f3ece4;
  --same-num: #eddcc8;
  --error: #e74c3c;
  --error-bg: #fde8e8;
  --given: #3d3229;
  --player: #6b89a8;
  --border: #d4c8bb;
  --border-thick: #8a7d72;
  --notes-color: #a09080;
  --btn-bg: #f0e8de;
  --btn-active: #c9956b;
  --btn-active-text: #fff;
  --success: #6bcb77;
  --shadow: 0 2px 20px rgba(90, 70, 50, 0.08);
  --radius: 18px;

  /* sizing tokens — overridden by media queries */
  --cell-font: 28px;
  --note-font: 10px;
  --num-font: 28px;
  --title-font: 32px;
  --diff-font: 16px;
  --stat-font: 18px;
  --action-font: 15px;
  --action-icon: 22px;
  --newgame-font: 18px;
}

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
  -webkit-tap-highlight-color: transparent;
  -webkit-touch-callout: none;
  user-select: none;
}

html, body {
  height: 100%;
  height: 100dvh;
  overflow: hidden;
}

body {
  font-family: -apple-system, 'PingFang TC', 'Noto Sans TC', 'Helvetica Neue', sans-serif;
  background: var(--bg);
  color: var(--text);
  display: flex;
  justify-content: center;
  align-items: stretch;
}

/* =============================================================
   Layout — the grid is king, everything else stays compact
   ============================================================= */

.app {
  width: 100%;
  max-width: 900px;
  height: 100%;
  height: 100dvh;
  padding: 16px 20px;
  padding-top: calc(16px + env(safe-area-inset-top, 0px));
  padding-bottom: calc(12px + env(safe-area-inset-bottom, 0px));
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 10px;
}

/* --- Header --- */

.header {
  width: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-shrink: 0;
}

.title {
  font-size: var(--title-font);
  font-weight: 700;
  color: var(--text);
  letter-spacing: 4px;
}

.header-right {
  display: flex;
  align-items: center;
  gap: 14px;
}

.help-btn {
  width: 44px;
  height: 44px;
  border-radius: 50%;
  border: 2px solid var(--border);
  background: var(--card);
  color: var(--text-light);
  font-size: 20px;
  font-weight: 600;
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  transition: all 0.2s;
}
.help-btn:hover { border-color: var(--accent); color: var(--accent); }

/* --- Status bar --- */

.status-bar {
  width: 100%;
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-shrink: 0;
}

.difficulty-bar {
  display: flex;
  gap: 8px;
}

.diff-btn {
  padding: 8px 20px;
  border: none;
  border-radius: 22px;
  background: var(--btn-bg);
  color: var(--text-light);
  font-size: var(--diff-font);
  font-weight: 500;
  cursor: pointer;
  transition: all 0.2s;
}
.diff-btn.active {
  background: var(--accent);
  color: var(--btn-active-text);
}

.stats {
  display: flex;
  gap: 18px;
  font-size: var(--stat-font);
  color: var(--text-light);
}

.stat-item {
  display: flex;
  align-items: center;
  gap: 5px;
}

.stat-icon {
  font-size: var(--stat-font);
}

/* =============================================================
   Grid — takes ALL remaining vertical space
   ============================================================= */

.grid-container {
  /* This is the key: flex-grow grabs all leftover height */
  flex: 1 1 0;
  /* Keep it square — width matches height */
  aspect-ratio: 1;
  /* But never wider than the screen */
  max-width: 100%;
  /* Center if narrower than parent */
  align-self: center;
  background: var(--card);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 4px;
  border: 3px solid var(--border-thick);
  /* prevent it from overflowing */
  min-height: 0;
}

.grid {
  display: grid;
  grid-template-columns: repeat(9, 1fr);
  grid-template-rows: repeat(9, 1fr);
  width: 100%;
  height: 100%;
  gap: 0;
}

.grid.loading {
  opacity: 0.3;
  pointer-events: none;
}

/* --- Cells --- */

.cell {
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: var(--cell-font);
  font-weight: 500;
  color: var(--player);
  border: 0.5px solid var(--border);
  cursor: pointer;
  transition: background 0.15s;
  position: relative;
}

.cell.given {
  color: var(--given);
  font-weight: 700;
}

.cell.selected {
  background: var(--selected);
}

.cell.highlight {
  background: var(--highlight);
}

.cell.same-num {
  background: var(--same-num);
}

.cell.error {
  color: var(--error);
  background: var(--error-bg);
}

/* 3x3 box borders */
.cell.box-left {
  border-left: 3px solid var(--border-thick);
}
.cell.box-top {
  border-top: 3px solid var(--border-thick);
}

/* grid edges */
.cell:nth-child(9n+1) { border-left: none; }
.cell:nth-child(-n+9)  { border-top: none; }
.cell:nth-child(9n)    { border-right: none; }
.cell:nth-last-child(-n+9) { border-bottom: none; }

/* Round corners */
.cell:nth-child(1)  { border-top-left-radius: calc(var(--radius) - 5px); }
.cell:nth-child(9)  { border-top-right-radius: calc(var(--radius) - 5px); }
.cell:nth-child(73) { border-bottom-left-radius: calc(var(--radius) - 5px); }
.cell:nth-child(81) { border-bottom-right-radius: calc(var(--radius) - 5px); }

/* --- Notes --- */

.cell.has-notes { padding: 0; }

.note-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  grid-template-rows: repeat(3, 1fr);
  width: 100%;
  height: 100%;
  align-items: center;
  justify-items: center;
}

.note-grid span {
  font-size: var(--note-font);
  color: var(--notes-color);
  font-weight: 500;
  line-height: 1;
}

/* --- Controls wrapper --- */

.controls {
  width: 100%;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 10px;
  flex-shrink: 0;
}

/* --- Numpad --- */

.numpad {
  display: grid;
  grid-template-columns: repeat(9, 1fr);
  gap: 6px;
  width: 100%;
}

.num-btn {
  aspect-ratio: 1;
  border: none;
  border-radius: 14px;
  background: var(--card);
  color: var(--text);
  font-size: var(--num-font);
  font-weight: 600;
  cursor: pointer;
  box-shadow: 0 1px 4px rgba(0,0,0,0.06);
  transition: all 0.15s;
  display: flex;
  align-items: center;
  justify-content: center;
}

.num-btn:active {
  transform: scale(0.93);
  background: var(--accent-light);
}

.num-btn.active-num {
  background: var(--accent);
  color: white;
}

.num-btn.num-done {
  opacity: 0.25;
  pointer-events: none;
}

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

.actions {
  display: flex;
  gap: 10px;
  width: 100%;
  justify-content: center;
  flex-shrink: 0;
}

.action-btn {
  flex: 1;
  max-width: 140px;
  padding: 10px 0;
  border: none;
  border-radius: 14px;
  background: var(--btn-bg);
  color: var(--text-light);
  font-size: var(--action-font);
  font-weight: 500;
  cursor: pointer;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 3px;
  transition: all 0.15s;
}

.action-btn:active {
  transform: scale(0.95);
}

.action-btn .icon {
  font-size: var(--action-icon);
}

.action-btn.active {
  background: var(--accent);
  color: white;
}

.new-game-btn {
  padding: 12px 32px;
  border: none;
  border-radius: 28px;
  background: var(--accent);
  color: white;
  font-size: var(--newgame-font);
  font-weight: 600;
  cursor: pointer;
  box-shadow: 0 3px 12px rgba(201, 149, 107, 0.3);
  transition: all 0.2s;
  letter-spacing: 1px;
  flex-shrink: 0;
}

.new-game-btn:active {
  transform: scale(0.96);
}

/* --- Modal --- */

.modal-overlay {
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, 0.4);
  backdrop-filter: blur(6px);
  display: flex;
  align-items: center;
  justify-content: center;
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.3s;
  z-index: 100;
}

.modal-overlay.show {
  opacity: 1;
  pointer-events: all;
}

.modal {
  background: var(--card);
  border-radius: 28px;
  padding: 44px;
  text-align: center;
  max-width: 480px;
  width: 85%;
  box-shadow: 0 10px 40px rgba(0, 0, 0, 0.15);
  transform: scale(0.9);
  transition: transform 0.3s;
}

.modal-overlay.show .modal {
  transform: scale(1);
}

.modal h2 {
  font-size: 32px;
  margin-bottom: 10px;
  color: var(--text);
}

.modal .subtitle {
  color: var(--text-light);
  margin-bottom: 28px;
  font-size: 19px;
}

.modal-stats {
  display: flex;
  justify-content: center;
  gap: 40px;
  margin-bottom: 32px;
}

.modal-stat { text-align: center; }

.modal-stat .label {
  font-size: 16px;
  color: var(--text-light);
  margin-bottom: 4px;
}

.modal-stat .value {
  font-size: 30px;
  font-weight: 700;
  color: var(--accent);
}

/* --- Help Modal --- */

.help-content {
  text-align: left;
  max-height: 60vh;
  overflow-y: auto;
  -webkit-overflow-scrolling: touch;
}

.help-content h3 {
  font-size: 21px;
  margin: 20px 0 10px;
  color: var(--accent);
}

.help-content h3:first-child { margin-top: 0; }

.help-content p {
  font-size: 18px;
  line-height: 1.7;
  color: var(--text);
  margin-bottom: 10px;
}

.help-content ul {
  padding-left: 22px;
  margin-bottom: 14px;
}

.help-content li {
  font-size: 18px;
  line-height: 1.8;
  color: var(--text);
}

.close-btn {
  margin-top: 24px;
  padding: 12px 40px;
  border: none;
  border-radius: 24px;
  background: var(--accent);
  color: white;
  font-size: 18px;
  font-weight: 600;
  cursor: pointer;
}

/* --- Confetti --- */

#confetti {
  position: fixed;
  top: 0; left: 0;
  width: 100%; height: 100%;
  pointer-events: none;
  z-index: 200;
  overflow: hidden;
}

.confetti-piece {
  position: absolute;
  top: -20px;
  width: 10px; height: 10px;
  border-radius: 2px;
  animation: confetti-fall linear forwards;
}

@keyframes confetti-fall {
  0%   { transform: translateY(0) rotate(0deg); opacity: 1; }
  100% { transform: translateY(100vh) rotate(720deg); opacity: 0; }
}

/* =============================================================
   TABLET PORTRAIT  (iPad mini 768 → iPad Pro 12.9" 1024)
   This is the primary play mode for mom.
   Grid fills ~60% of screen height, numbers are big and clear.
   ============================================================= */

@media (min-width: 748px) and (orientation: portrait) {
  :root {
    --cell-font: clamp(32px, 5.5vw, 52px);
    --note-font: clamp(12px, 1.8vw, 18px);
    --num-font: clamp(30px, 5vw, 48px);
    --title-font: 44px;
    --diff-font: 22px;
    --stat-font: 24px;
    --action-font: 20px;
    --action-icon: 30px;
    --newgame-font: 24px;
  }

  .app {
    max-width: 100%;
    padding: 20px 36px;
    padding-top: calc(20px + env(safe-area-inset-top, 0px));
    padding-bottom: calc(16px + env(safe-area-inset-bottom, 0px));
    gap: 12px;
  }

  .title { letter-spacing: 8px; }
  .help-btn { width: 52px; height: 52px; font-size: 26px; }
  .diff-btn { padding: 14px 30px; border-radius: 26px; }
  .stats { gap: 28px; }

  .grid-container {
    border: 4px solid var(--border-thick);
    border-radius: 22px;
    padding: 5px;
  }
  .cell.box-left { border-left: 4px solid var(--border-thick); }
  .cell.box-top  { border-top: 4px solid var(--border-thick); }

  .numpad { gap: 10px; }
  .num-btn { border-radius: 16px; aspect-ratio: 1; }
  .actions { gap: 14px; }
  .action-btn { max-width: 170px; padding: 14px 0; border-radius: 16px; gap: 5px; }
  .new-game-btn { padding: 16px 48px; border-radius: 32px; }

  .modal { max-width: 520px; padding: 48px; border-radius: 32px; }
  .modal h2 { font-size: 36px; }
  .modal .subtitle { font-size: 22px; }
  .modal-stat .label { font-size: 18px; }
  .modal-stat .value { font-size: 36px; }
  .help-content h3 { font-size: 24px; }
  .help-content p, .help-content li { font-size: 20px; }
  .close-btn { font-size: 20px; padding: 14px 48px; }
}

/* =============================================================
   LARGE TABLET PORTRAIT  (iPad Pro 12.9" — 1024px+)
   ============================================================= */

@media (min-width: 1024px) and (orientation: portrait) {
  :root {
    --cell-font: clamp(40px, 4.5vw, 58px);
    --note-font: clamp(14px, 1.6vw, 20px);
    --num-font: clamp(36px, 4.5vw, 54px);
    --title-font: 52px;
    --diff-font: 26px;
    --stat-font: 28px;
    --action-font: 24px;
    --action-icon: 34px;
    --newgame-font: 28px;
  }

  .app {
    padding: 28px 48px;
    padding-top: calc(28px + env(safe-area-inset-top, 0px));
    padding-bottom: calc(20px + env(safe-area-inset-bottom, 0px));
    gap: 16px;
  }

  .help-btn { width: 58px; height: 58px; font-size: 30px; }
  .diff-btn { padding: 16px 36px; border-radius: 28px; }

  .grid-container {
    border-width: 5px;
    border-radius: 24px;
    padding: 6px;
  }
  .cell.box-left { border-left-width: 5px; }
  .cell.box-top  { border-top-width: 5px; }
  .cell { border-width: 1px; }

  .numpad { gap: 12px; }
  .num-btn { border-radius: 18px; }
  .action-btn { max-width: 200px; padding: 16px 0; border-radius: 18px; }
  .new-game-btn { padding: 20px 56px; border-radius: 36px; }

  .modal { max-width: 600px; padding: 56px; }
  .modal h2 { font-size: 42px; }
  .modal .subtitle { font-size: 26px; }
  .modal-stat .label { font-size: 22px; }
  .modal-stat .value { font-size: 42px; }
  .help-content h3 { font-size: 28px; }
  .help-content p, .help-content li { font-size: 24px; line-height: 1.8; }
  .close-btn { font-size: 24px; padding: 16px 56px; border-radius: 28px; }
}

/* =============================================================
   TABLET LANDSCAPE  — grid left, controls right
   ============================================================= */

@media (min-width: 700px) and (orientation: landscape) {
  :root {
    --cell-font: clamp(24px, 6.5vh, 46px);
    --note-font: clamp(10px, 2vh, 16px);
    --num-font: clamp(28px, 6vh, 44px);
    --title-font: 34px;
    --diff-font: 20px;
    --stat-font: 22px;
    --action-font: 19px;
    --action-icon: 28px;
    --newgame-font: 22px;
  }

  .app {
    /* Two-column: header/status span full width, then grid + controls side by side */
    display: grid;
    grid-template-columns: 1fr auto;
    grid-template-rows: auto auto 1fr;
    align-items: start;
    max-width: 100%;
    padding: 12px 24px;
    padding-left: calc(24px + env(safe-area-inset-left, 0px));
    padding-right: calc(24px + env(safe-area-inset-right, 0px));
    padding-top: calc(12px + env(safe-area-inset-top, 0px));
    padding-bottom: calc(12px + env(safe-area-inset-bottom, 0px));
    gap: 10px 24px;
  }

  .header {
    grid-column: 1 / -1;
  }

  .status-bar {
    grid-column: 1 / -1;
  }

  /* Grid: fill all remaining height, stay square */
  .grid-container {
    grid-column: 1;
    grid-row: 3;
    align-self: stretch;
    /* height is driven by the row; keep square via aspect-ratio */
    aspect-ratio: 1;
    max-width: 100%;
    /* don't let it exceed the available height */
    max-height: calc(100dvh - 110px);
    border: 4px solid var(--border-thick);
  }
  .cell.box-left { border-left: 4px solid var(--border-thick); }
  .cell.box-top  { border-top: 4px solid var(--border-thick); }

  /* Controls: right column, vertically centered */
  .controls {
    grid-column: 2;
    grid-row: 3;
    align-self: center;
    width: auto;
    min-width: 280px;
    max-width: 360px;
    gap: 16px;
  }

  .numpad {
    grid-template-columns: repeat(3, 1fr);
    gap: 12px;
  }
  .num-btn {
    aspect-ratio: 1.2;
    border-radius: 16px;
  }

  .actions {
    flex-wrap: wrap;
    gap: 10px;
    justify-content: center;
  }
  .action-btn {
    flex: 0 0 calc(50% - 6px);
    max-width: none;
    padding: 14px 0;
    border-radius: 16px;
  }

  .new-game-btn { padding: 16px 40px; }
}

/* =============================================================
   SMALL PHONES
   ============================================================= */

@media (max-width: 380px) {
  :root {
    --cell-font: 20px;
    --note-font: 8px;
    --num-font: 22px;
    --title-font: 24px;
    --diff-font: 13px;
    --stat-font: 14px;
    --action-font: 12px;
    --action-icon: 18px;
    --newgame-font: 15px;
  }
  .app { padding: 10px 12px; gap: 8px; }
  .diff-btn { padding: 5px 12px; }
}