/* Sudoku Zen — layout, grid, panel, pad. Blue-on-white palette. */

:root {
  --sudoku-blue: #4a5fc1;
  --sudoku-blue-dark: #3b4ca0;
  --sudoku-blue-tint: #edf0fb;
  --sudoku-blue-hover: #dde3f5;
  --sudoku-border: #bfc7d9;
  --sudoku-border-thin: #e4e8f0;
  --sudoku-text: #1b2545;
  --sudoku-muted: #8891aa;
  --sudoku-wrong: #d94e4e;
  --sudoku-box-alt: #f5f7fb;
}

body { background: #ffffff; color: var(--sudoku-text); }

.sudoku-page {
  position: relative;
  max-width: 1100px;
  margin: 0 auto;
  padding: var(--space-lg) var(--space-md);
}

.page-header {
  display: flex;
  align-items: center;
  gap: var(--space-md);
  margin-bottom: var(--space-lg);
}
.back-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 40px; height: 40px;
  border-radius: 50%;
  color: var(--sudoku-text);
  transition: background 120ms;
}
.back-btn:hover { background: var(--sudoku-blue-tint); }
.page-header h1 { margin: 0; font-size: 1.5rem; font-weight: 600; }

.sudoku-layout {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--space-xl);
  align-items: start;
}

@media (min-width: 900px) {
  .sudoku-layout {
    grid-template-columns: max-content 360px;
    gap: var(--space-2xl);
    justify-content: center;
  }
}

/* Difficulty bar — desktop is single line; mobile wraps with label on its own row */
.difficulty-bar {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  gap: var(--space-md);
  margin-bottom: var(--space-md);
  font-size: 0.95rem;
}
.difficulty-label {
  color: var(--sudoku-muted);
  font-weight: 500;
  flex-basis: 100%;
}
@media (min-width: 600px) {
  .difficulty-label { flex-basis: auto; }
}
.difficulty-btn {
  background: transparent;
  border: none;
  padding: 0;
  font: inherit;
  color: var(--sudoku-muted);
  cursor: pointer;
  font-weight: 500;
  transition: color 120ms;
}
.difficulty-btn:hover { color: var(--sudoku-text); }
.difficulty-btn.is-active { color: var(--sudoku-blue); font-weight: 700; }
.difficulty-btn:focus-visible { outline: 2px solid var(--sudoku-blue); outline-offset: 4px; border-radius: 3px; }

@media (max-width: 599px) {
  .difficulty-bar { gap: var(--space-xs) var(--space-sm); }
  .difficulty-btn { font-size: 0.875rem; }
}

/* Board */
.board-column { min-width: 0; }
.board-frame {
  position: relative;
  display: inline-block;
  width: 100%;
}
.grid {
  --cell: min(11vw, 60px);
  display: grid;
  grid-template-columns: repeat(9, var(--cell));
  grid-template-rows: repeat(9, var(--cell));
  background: #ffffff;
  border: 2px solid var(--sudoku-border);
  border-radius: 4px;
  margin: 0;
  user-select: none;
  touch-action: manipulation;
}

.cell {
  position: relative;
  border: none;
  border-right: 1px solid var(--sudoku-border-thin);
  border-bottom: 1px solid var(--sudoku-border-thin);
  background: #ffffff;
  padding: 0;
  font: inherit;
  font-size: calc(var(--cell) * 0.5);
  font-weight: 400;
  color: var(--sudoku-text);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: background 80ms;
}
.cell:last-child, .cell:nth-child(9n) { border-right: none; }
.cell.bx-left { border-left: 2px solid var(--sudoku-border); }
.cell.bx-top { border-top: 2px solid var(--sudoku-border); }
.cell.box-alt { background: var(--sudoku-box-alt); }
.cell.clue { font-weight: 500; color: var(--sudoku-text); }
.cell.peer { background: var(--sudoku-blue-tint); }
.cell.box-alt.peer { background: #e4ebf9; }
.cell.same-value { background: #c8d2ef; }
.cell.same-value .cell-value { font-weight: 700; color: var(--sudoku-blue-dark); }
.cell.selected { background: #c8d2ef !important; }
.cell.wrong .cell-value { color: var(--sudoku-wrong); }

.cell-value {
  position: absolute;
  inset: 0;
  line-height: 1;
  display: flex;
  align-items: center;
  justify-content: center;
}
.cell-notes {
  position: absolute;
  inset: 0;
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  grid-template-rows: repeat(3, 1fr);
  padding: 6%;
  font-size: calc(var(--cell) * 0.22);
  color: var(--sudoku-muted);
  font-weight: 500;
  line-height: 1;
  gap: 0;
}
.cell-notes[hidden] { display: none; }
.cell-note {
  display: flex;
  align-items: center;
  justify-content: center;
  min-width: 0;
  min-height: 0;
}

.pause-overlay {
  position: absolute;
  inset: 0;
  background: rgba(255,255,255,0.94);
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: var(--space-sm);
  color: var(--sudoku-blue);
  border-radius: 4px;
  z-index: 2;
}
.pause-overlay[hidden] { display: none; }
.pause-overlay p { margin: 0; font-size: 1.125rem; font-weight: 600; }

/* Panel */
.panel-column {
  display: flex;
  flex-direction: column;
  gap: var(--space-lg);
  min-width: 0;
}

.panel-head {
  display: grid;
  grid-template-columns: 1fr auto 1fr auto;
  align-items: center;
  gap: var(--space-md);
}
.stat { display: flex; flex-direction: column; gap: 2px; }
.stat-right { align-items: flex-end; text-align: right; }
.stat-counter { align-items: center; text-align: center; }
.stat-label {
  font-size: 0.75rem;
  color: var(--sudoku-muted);
  text-transform: none;
  letter-spacing: 0;
}
.stat-value {
  font-size: 1rem;
  font-weight: 600;
  color: var(--sudoku-text);
  font-variant-numeric: tabular-nums;
}
.stat-value.big {
  font-size: 1.5rem;
  font-weight: 700;
}

/* Action row (icon buttons) */
.action-row {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: var(--space-md);
  justify-items: center;
}
.icon-btn {
  position: relative;
  width: 52px; height: 52px;
  border-radius: 50%;
  border: none;
  background: var(--sudoku-blue-tint);
  color: var(--sudoku-blue);
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  transition: background 120ms, transform 80ms;
}
.icon-btn:hover { background: var(--sudoku-blue-hover); }
.icon-btn:active { transform: scale(0.96); }
.icon-btn.is-active { background: var(--sudoku-blue); color: #ffffff; }
.icon-btn.small { width: 32px; height: 32px; }
.icon-btn:focus-visible { outline: 2px solid var(--sudoku-blue); outline-offset: 2px; }

.indicator {
  position: absolute;
  top: -4px; right: -4px;
  font-size: 0.55rem;
  font-weight: 700;
  background: var(--sudoku-muted);
  color: #ffffff;
  padding: 2px 5px;
  border-radius: 10px;
  line-height: 1;
  letter-spacing: 0.04em;
}
.icon-btn.is-active .indicator { background: var(--sudoku-blue-dark); }
.badge {
  position: absolute;
  top: -4px; right: -4px;
  min-width: 20px; height: 20px;
  border-radius: 50%;
  background: var(--sudoku-blue);
  color: #ffffff;
  font-size: 0.7rem;
  font-weight: 700;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 0 6px;
}

/* Number pad */
.number-pad {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--space-sm);
}
.pad-btn {
  aspect-ratio: 1 / 1;
  border: none;
  background: var(--sudoku-blue-tint);
  color: var(--sudoku-blue);
  font-size: 2rem;
  font-weight: 400;
  cursor: pointer;
  border-radius: 10px;
  transition: background 120ms, transform 80ms;
  font-family: inherit;
}
.pad-btn:hover { background: var(--sudoku-blue-hover); }
.pad-btn:active { transform: scale(0.97); }
.pad-btn:focus-visible { outline: 2px solid var(--sudoku-blue); outline-offset: 2px; }
.pad-btn.is-hidden { visibility: hidden; pointer-events: none; }

/* New Game CTA */
.new-game-btn {
  width: 100%;
  padding: var(--space-md) var(--space-lg);
  border: none;
  border-radius: 12px;
  background: var(--sudoku-blue);
  color: #ffffff;
  font-size: 1.125rem;
  font-weight: 600;
  cursor: pointer;
  transition: background 120ms, transform 80ms;
  font-family: inherit;
}
.new-game-btn:hover { background: var(--sudoku-blue-dark); }
.new-game-btn:active { transform: translateY(1px); }
.new-game-btn:focus-visible { outline: 2px solid var(--sudoku-blue-dark); outline-offset: 2px; }

/* Ad placeholders — replace with AdSense units in week 3 */
.ad-label {
  display: block;
  font-size: 0.6875rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--sudoku-muted);
  margin-bottom: var(--space-xs);
  text-align: center;
}
.ad-unit {
  display: flex;
  align-items: center;
  justify-content: center;
  background: var(--sudoku-blue-tint);
  color: var(--sudoku-blue);
  border-radius: 6px;
  font-size: 0.875rem;
  font-weight: 500;
  border: 1px dashed var(--sudoku-border);
}
.ad-300x600 { width: 300px; height: 600px; }
.ad-728x90 { width: 100%; max-width: 728px; height: 90px; margin: 0 auto; }

/* Bottom ad slot (leaderboard) */
.ad-slot {
  margin: var(--space-lg) auto var(--space-md);
  padding: 0;
  max-width: 728px;
}

/* Footer */
.game-footer {
  margin: var(--space-lg) auto 0;
  padding-top: var(--space-md);
  border-top: 1px solid var(--sudoku-border-thin);
  text-align: center;
  font-size: 0.8125rem;
  color: var(--sudoku-muted);
  display: flex;
  justify-content: center;
  align-items: center;
  gap: var(--space-sm);
  flex-wrap: wrap;
  max-width: 728px;
}
.game-footer a { color: var(--sudoku-muted); text-decoration: none; }
.game-footer a:hover { color: var(--sudoku-text); text-decoration: underline; }

/* Side rails — only on viewports ≥1500px where 300×600 ads can sit outside the 1100px content column without overlap. */
.side-ad { display: none; }

@media (min-width: 1500px) {
  .side-ad {
    display: block;
    width: 300px;
    z-index: 5;
    top: 120px;
    position: fixed;
  }
  .side-ad .ad-300x600 { width: 300px; height: 600px; }
  .side-ad-left { left: calc((100vw - 1100px) / 2 - 340px); }
  .side-ad-right { right: calc((100vw - 1100px) / 2 - 340px); }
}

/* Modal */
.modal {
  position: fixed;
  inset: 0;
  background: rgba(27, 37, 69, 0.5);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 100;
  padding: var(--space-md);
}
.modal[hidden] { display: none; }
.modal-card {
  background: #ffffff;
  border-radius: 16px;
  padding: var(--space-xl);
  max-width: 360px;
  width: 100%;
  text-align: center;
  box-shadow: 0 20px 40px rgba(27, 37, 69, 0.2);
}
.modal-card h2 { margin: 0 0 var(--space-xs); font-size: 1.75rem; }
.modal-card p { margin: 0 0 var(--space-md); color: var(--sudoku-muted); }
.modal-card .time {
  font-size: 2.5rem;
  font-weight: 700;
  color: var(--sudoku-blue);
  font-variant-numeric: tabular-nums;
  margin-bottom: var(--space-lg);
}

/* Mobile tweaks */
@media (max-width: 899px) {
  .sudoku-page { padding: var(--space-md) var(--space-md); }
  .page-header { margin-bottom: var(--space-md); }
  .sudoku-layout { gap: var(--space-md); }
  .panel-column { gap: var(--space-md); }
  .grid { --cell: min(calc((100vw - 2rem) / 9), 50px); }
  .action-row { grid-template-columns: repeat(4, 52px); justify-content: center; gap: var(--space-sm); }
  .panel-head { grid-template-columns: 1fr auto 1fr auto; }
  .number-pad { max-width: 380px; margin: 0 auto; gap: var(--space-xs); }
  .pad-btn { font-size: 1.5rem; }
  .new-game-btn { max-width: 380px; margin: 0 auto; display: block; padding: var(--space-sm) var(--space-md); }
  .ad-slot { margin-top: var(--space-md); }
}

@media (min-width: 900px) {
  .grid { --cell: 56px; }
  .pad-btn { font-size: 2.25rem; }
}

@media (min-width: 1100px) {
  .grid { --cell: 62px; }
}