/* ============================================================
 * 1. Custom properties
 * ============================================================ */
:root {
  --color-brand: #1D9E75;
  --color-brand-light: #9FE1CB;
  --color-brand-dark: #0F6E56;
  --color-given: #1a1a1a;
  --color-player: #1D9E75;
  --color-invalid: #E24B4A;
  --color-selected: #E1F5EE;
  --color-peer: #f0f9f6;
  --color-border-light: #ccc;
  --color-border-dark: #333;
  --color-bg: #f8f8f6;
  --color-surface: #ffffff;
  --color-text: #1a1a1a;
  --color-text-muted: #666;

  --radius-sm: 6px;
  --radius-md: 10px;
  --space-xs: 4px;
  --space-sm: 8px;
  --space-md: 12px;
  --space-lg: 16px;

  --transition-fast: 120ms ease-out;

  --touch-target: 44px;
  --focus-ring: 0 0 0 3px rgba(29, 158, 117, 0.45);

  /* Hint highlights — strengths from subtle (level 1) to strong (level 4). */
  --color-hint-region:    #E1F5EE;  /* light brand green */
  --color-hint-target:    #9FE1CB;  /* medium brand green */
  --color-hint-technique: #FFF3CD;  /* soft amber */
  --color-hint-filled:    #1D9E75;  /* brand green — strong */
}

/* ============================================================
 * 2. Layout
 * ============================================================ */
.game-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: var(--space-md) var(--space-lg);
  background: var(--color-surface);
  border-bottom: 1px solid var(--color-border-light);
}

.game-header__brand {
  font-weight: 700;
  color: var(--color-brand-dark);
  text-decoration: none;
  font-size: 1.1rem;
}

.game-header__nav a {
  color: var(--color-text-muted);
  text-decoration: none;
  font-size: 0.95rem;
}

.game-main {
  max-width: 560px;
  margin: 0 auto;
  padding: var(--space-md);
  display: flex;
  flex-direction: column;
  gap: var(--space-md);
  background: var(--color-bg);
  min-height: calc(100vh - 60px);
  box-sizing: border-box;
}

.game-title {
  font-size: 1.35rem;
  margin: 0;
  color: var(--color-text);
}

.game-meta {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-md);
  font-size: 1rem;
  color: var(--color-text);
}

.game-meta__item {
  display: inline-flex;
  align-items: center;
  gap: var(--space-xs);
}

.game-meta__timer {
  font-variant-numeric: tabular-nums;
  font-weight: 600;
  font-size: 1.1rem;
}

/* ---- Timer toggle (hide/show display) -------------------- */

.game-meta__timer-group {
  position: relative;
}

.timer-toggle {
  appearance: none;
  background: transparent;
  border: none;
  color: var(--color-text-muted);
  cursor: pointer;
  padding: 4px 6px;
  font-size: 0.9rem;
  border-radius: var(--radius-sm);
  line-height: 1;
  display: inline-flex;
  align-items: center;
  justify-content: center;
}

.timer-toggle:hover {
  color: var(--color-text);
  background: var(--color-peer);
}

.timer-toggle:focus-visible {
  outline: none;
  box-shadow: var(--focus-ring);
}

/* Default: show eye icon, hide eye-slash. When group has
   .timer-hidden, swap. */
.timer-toggle-hide { display: none; }
.game-meta__timer-group.timer-hidden .timer-toggle-show { display: none; }
.game-meta__timer-group.timer-hidden .timer-toggle-hide { display: inline; }

/* When hidden, mask the numeric display with em-dashes while keeping
   the layout stable. sudoku.js keeps writing the elapsed time to the
   underlying span — we just cover it visually. tabular-nums keeps the
   em-dash alignment consistent with the real timer. */
.game-meta__timer-group.timer-hidden .game-meta__timer {
  color: transparent;
  user-select: none;
  position: relative;
}

.game-meta__timer-group.timer-hidden .game-meta__timer::after {
  content: '\2014\2009:\2009\2014';
  position: absolute;
  inset: 0;
  color: var(--color-text-muted);
  display: flex;
  align-items: center;
  justify-content: center;
  font-variant-numeric: tabular-nums;
}

.pencil-indicator {
  color: var(--color-text-muted);
  opacity: 0.35;
  transition: opacity var(--transition-fast), color var(--transition-fast);
}

body.is-pencil-mode .pencil-indicator {
  opacity: 1;
  color: var(--color-brand-dark);
}

/* ============================================================
 * 3. Grid
 * ============================================================ */
.sudoku-grid {
  position: relative;
  display: grid;
  grid-template-columns: repeat(9, 1fr);
  grid-template-rows: repeat(9, 1fr);
  width: 100%;
  aspect-ratio: 1 / 1;
  max-width: min(100%, 480px);
  margin: 0 auto;
  background: var(--color-surface);
  border: 3px solid var(--color-border-dark);
  box-sizing: border-box;
  user-select: none;
  touch-action: manipulation;
}

.sudoku-cell {
  position: relative;
  appearance: none;
  background: var(--color-surface);
  border: 1px solid var(--color-border-light);
  padding: 0;
  margin: 0;
  font-family: inherit;
  font-size: clamp(1rem, 5vw, 1.6rem);
  color: var(--color-given);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  min-width: 0;
  min-height: 0;
  aspect-ratio: 1 / 1;
  transition: background-color var(--transition-fast);
}

.sudoku-cell:focus {
  outline: none;
  box-shadow: inset 0 0 0 3px var(--color-brand);
  z-index: 2;
}

.sudoku-cell--box-left  { border-left:  2px solid var(--color-border-dark); }
.sudoku-cell--box-top   { border-top:   2px solid var(--color-border-dark); }

.sudoku-cell--player { color: var(--color-player); font-weight: 600; }
.sudoku-cell--given  { color: var(--color-given);  font-weight: 700; cursor: default; }
.sudoku-cell--peer   { background-color: var(--color-peer); }
.sudoku-cell--same   { background-color: var(--color-brand-light); }
.sudoku-cell--selected {
  background-color: var(--color-selected);
  box-shadow: inset 0 0 0 2px var(--color-brand);
  z-index: 1;
}
.sudoku-cell--invalid { color: var(--color-invalid); }

/* Hint highlighting — additive on top of the base cell classes. */
.sudoku-cell--hint-region    { background-color: var(--color-hint-region); }
.sudoku-cell--hint-technique { background-color: var(--color-hint-technique); }
.sudoku-cell--hint-target {
  background-color: var(--color-hint-target);
  box-shadow: inset 0 0 0 2px var(--color-brand);
}
.sudoku-cell--hint-filled {
  background-color: var(--color-hint-filled);
  color: var(--color-surface) !important;
  box-shadow: inset 0 0 0 2px var(--color-brand-dark);
}

.sudoku-cell__digit {
  line-height: 1;
  display: inline-block;
}

.sudoku-cell__notes {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  grid-template-rows: repeat(3, 1fr);
  width: 100%;
  height: 100%;
  padding: 2px;
  box-sizing: border-box;
  font-size: clamp(0.5rem, 1.9vw, 0.72rem);
  color: var(--color-text-muted);
  font-weight: 500;
}

.sudoku-cell__note {
  display: flex;
  align-items: center;
  justify-content: center;
  line-height: 1;
}

body.is-paused .sudoku-cell__digit,
body.is-paused .sudoku-cell__notes { visibility: hidden; }

body.is-paused .sudoku-grid::after {
  content: "Paused";
  position: absolute;
  inset: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.75rem;
  font-weight: 700;
  color: var(--color-brand-dark);
  background: var(--color-surface);
  pointer-events: none;
}

/* ============================================================
 * 4. Number pad
 * ============================================================ */
.sudoku-numpad {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--space-sm);
  max-width: 320px;
  width: 100%;
  margin: 0 auto;
}

.numpad-btn {
  appearance: none;
  min-height: var(--touch-target);
  min-width: var(--touch-target);
  padding: var(--space-md);
  font-size: 1.35rem;
  font-weight: 600;
  color: var(--color-text);
  background: var(--color-surface);
  border: 1px solid var(--color-border-light);
  border-radius: var(--radius-sm);
  cursor: pointer;
  font-family: inherit;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-xs);
  transition: background-color var(--transition-fast), transform var(--transition-fast);
}

.numpad-btn:hover { background: var(--color-peer); }
.numpad-btn:active {
  transform: scale(0.97);
  background: var(--color-brand-light);
}
.numpad-btn:focus-visible {
  outline: none;
  box-shadow: var(--focus-ring);
}

.numpad-btn--clear {
  grid-column: 1 / -1;
  background: var(--color-bg);
  color: var(--color-text-muted);
  font-size: 1rem;
  font-weight: 500;
}

body.is-pencil-mode .numpad-btn {
  border-color: var(--color-brand);
  color: var(--color-brand-dark);
}

/* ============================================================
 * 5. Action buttons
 * ============================================================ */
.sudoku-actions {
  display: grid;
  grid-template-columns: repeat(5, 1fr);
  gap: var(--space-sm);
  max-width: 560px;
  width: 100%;
  margin: 0 auto;
}

@media (max-width: 400px) {
  .sudoku-actions {
    /* On narrow phones, let hint wrap to the next row rather than
       squeezing the icons. */
    grid-template-columns: repeat(3, 1fr);
  }
}

.action-btn {
  appearance: none;
  min-height: var(--touch-target);
  padding: var(--space-sm) var(--space-sm);
  font-size: 1rem;
  font-weight: 600;
  color: var(--color-text);
  background: var(--color-surface);
  border: 1px solid var(--color-border-light);
  border-radius: var(--radius-sm);
  cursor: pointer;
  font-family: inherit;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-xs);
  transition: background-color var(--transition-fast), transform var(--transition-fast);
}

.action-btn i { pointer-events: none; }
.action-btn:hover { background: var(--color-peer); }
.action-btn:active { transform: scale(0.97); }
.action-btn:focus-visible {
  outline: none;
  box-shadow: var(--focus-ring);
}

.action-btn--active {
  background: var(--color-brand);
  color: var(--color-surface);
  border-color: var(--color-brand-dark);
}

.action-btn--primary {
  background: var(--color-brand);
  color: var(--color-surface);
  border-color: var(--color-brand-dark);
}

.sudoku-controls {
  display: flex;
  flex-direction: column;
  gap: var(--space-md);
}

/* ============================================================
 * 6. Difficulty selector
 * ============================================================ */
.sudoku-difficulty-selector {
  position: fixed;
  inset: 0;
  background: rgba(15, 30, 24, 0.6);
  display: flex;
  align-items: center;
  justify-content: center;
  padding: var(--space-lg);
  z-index: 10;
}
.sudoku-difficulty-selector[hidden] { display: none; }

.sudoku-difficulty-selector__panel {
  background: var(--color-surface);
  border-radius: var(--radius-md);
  padding: var(--space-lg);
  max-width: 420px;
  width: 100%;
  box-shadow: 0 12px 32px rgba(0, 0, 0, 0.25);
  display: flex;
  flex-direction: column;
  gap: var(--space-md);
}

.sudoku-difficulty-selector__heading {
  margin: 0;
  font-size: 1.25rem;
  color: var(--color-brand-dark);
  text-align: center;
}

.sudoku-difficulty-selector__list {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--space-sm);
}

.difficulty-card {
  appearance: none;
  padding: var(--space-md);
  background: var(--color-bg);
  border: 2px solid var(--color-border-light);
  border-radius: var(--radius-md);
  cursor: pointer;
  font-family: inherit;
  min-height: 72px;
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  justify-content: center;
  gap: var(--space-xs);
  text-align: left;
  transition: border-color var(--transition-fast), transform var(--transition-fast), background-color var(--transition-fast);
}

.difficulty-card:hover {
  border-color: var(--color-brand);
  background: var(--color-peer);
}
.difficulty-card:active { transform: scale(0.98); }
.difficulty-card:focus-visible {
  outline: none;
  box-shadow: var(--focus-ring);
}

.difficulty-card__label {
  font-size: 1.05rem;
  font-weight: 700;
  color: var(--color-text);
}
.difficulty-card__desc {
  font-size: 0.85rem;
  color: var(--color-text-muted);
}

.difficulty-card__cancel {
  appearance: none;
  padding: var(--space-sm) var(--space-md);
  background: transparent;
  color: var(--color-text-muted);
  border: 1px solid var(--color-border-light);
  border-radius: var(--radius-sm);
  cursor: pointer;
  font-family: inherit;
  font-size: 1rem;
  min-height: var(--touch-target);
}
.difficulty-card__cancel:hover { background: var(--color-peer); }
.difficulty-card__cancel:focus-visible {
  outline: none;
  box-shadow: var(--focus-ring);
}

/* ============================================================
 * 7. Completion overlay
 * ============================================================ */
.sudoku-completion {
  position: fixed;
  inset: 0;
  background: rgba(15, 110, 86, 0.8);
  display: flex;
  align-items: center;
  justify-content: center;
  padding: var(--space-lg);
  z-index: 9;
}
.sudoku-completion[hidden] { display: none; }

.sudoku-completion__inner {
  background: var(--color-surface);
  padding: var(--space-lg);
  border-radius: var(--radius-md);
  text-align: center;
  min-width: 260px;
  max-width: 380px;
  width: 100%;
  box-shadow: 0 12px 32px rgba(0, 0, 0, 0.25);
  animation: popIn 240ms ease-out;
}
.sudoku-completion__inner h2 {
  margin: 0 0 var(--space-sm);
  color: var(--color-brand-dark);
}
.sudoku-completion__inner p {
  margin: 0 0 var(--space-md);
  font-size: 1.1rem;
  color: var(--color-text);
}

/* Loading overlay */
.sudoku-loading {
  position: fixed;
  inset: 0;
  background: rgba(15, 30, 24, 0.6);
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: var(--space-lg);
  z-index: 11;
  color: var(--color-surface);
  font-size: 1.1rem;
  font-weight: 600;
}
.sudoku-loading[hidden] { display: none; }

.sudoku-loading::before {
  content: "";
  width: 40px;
  height: 40px;
  border: 4px solid rgba(255, 255, 255, 0.3);
  border-top-color: var(--color-surface);
  border-radius: 50%;
  animation: spin 0.8s linear infinite;
}

@keyframes spin {
  to { transform: rotate(360deg); }
}

/* Screen reader only live region */
.sudoku-status {
  position: absolute;
  left: -9999px;
  width: 1px;
  height: 1px;
  overflow: hidden;
}

/* ============================================================
 * 8. Animations
 * ============================================================ */
@keyframes popIn {
  0%   { transform: scale(0.9); opacity: 0; }
  100% { transform: scale(1);   opacity: 1; }
}

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

/* ============================================================
 * 9. Media queries
 * ============================================================ */
@media (min-width: 768px) {
  .game-main {
    max-width: 900px;
    display: grid;
    grid-template-columns: minmax(0, 1fr) 320px;
    grid-template-areas:
      "title  title"
      "meta   meta"
      "grid   controls"
      "load   load";
    gap: var(--space-lg);
    align-items: start;
  }
  .game-title     { grid-area: title; }
  .game-meta      { grid-area: meta; }
  .sudoku-grid    { grid-area: grid; max-width: 520px; }
  .sudoku-controls { grid-area: controls; }
  .sudoku-loading { grid-area: load; }
}

@media (min-width: 1024px) {
  .sudoku-grid { max-width: 560px; }
}