/* ===== Game Screen ===== */
#screen-game {
  background: var(--bg);
}

/* ===== Game Header ===== */
.game-header {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 12px 16px;
  background: var(--surface);
  border-bottom: 1px solid var(--border);
  flex-shrink: 0;
}

.game-info-bar {
  display: flex;
  flex: 1;
  justify-content: center;
  gap: 16px;
}

.info-item {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 2px;
}

.info-label {
  font-size: 0.7rem;
  color: var(--text-secondary);
  text-transform: uppercase;
  letter-spacing: 0.5px;
  font-weight: 500;
}

.info-value {
  font-size: 0.95rem;
  font-weight: 600;
  color: var(--text);
}

.score-row {
  display: flex;
  align-items: center;
  gap: 5px;
}

.streak-badge {
  display: inline-flex;
  align-items: center;
  font-size: 0.68rem;
  font-weight: 700;
  padding: 1px 5px;
  border-radius: 8px;
  line-height: 1.2;
  transition: all 0.2s ease;
}

.streak-badge.hidden {
  display: none;
}

.streak-badge.tier-1 {
  background: #FEF3C7;
  color: #D97706;
}

.streak-badge.tier-2 {
  background: #FFEDD5;
  color: #EA580C;
}

.streak-badge.tier-3 {
  background: #FEE2E2;
  color: #DC2626;
}

.streak-badge.tier-4 {
  background: #F3E8FF;
  color: #7C3AED;
  box-shadow: 0 0 6px rgba(124, 58, 237, 0.25);
}

.mistake-row {
  display: flex;
  align-items: center;
  gap: 5px;
}

.timer-row {
  display: flex;
  align-items: center;
  gap: 4px;
}

.timer-row svg {
  width: 14px;
  height: 14px;
  color: var(--text-secondary);
}

.mistake-display.has-errors {
  color: var(--error);
}

.mistake-warning {
  color: var(--warning) !important;
  font-weight: 700;
}

.mistake-danger {
  color: var(--error) !important;
  font-weight: 700;
  animation: shake 0.4s ease;
}

@keyframes shake {
  0%, 100% { transform: translateX(0); }
  25% { transform: translateX(-3px); }
  75% { transform: translateX(3px); }
}

.btn-text-sm {
  font-size: 0.8rem;
  padding: 6px 12px;
  background: none;
  border: none;
  color: var(--text-secondary);
  font-weight: 500;
  cursor: pointer;
  border-radius: var(--radius-sm);
  transition: all 0.2s ease;
}

.btn-text-sm:hover {
  background: var(--highlight-row);
  color: var(--text);
}

.btn-danger-sm {
  color: var(--error);
  font-size: 0.8rem;
  padding: 6px 12px;
  background: none;
  border: none;
  font-weight: 500;
  cursor: pointer;
  border-radius: var(--radius-sm);
  transition: all 0.2s ease;
}

.btn-danger-sm:hover {
  background: #FEE2E2;
}

/* ========================================
   GAME BODY
   ======================================== */
.game-body {
  flex: 1;
  display: flex;
  flex-direction: row;
  align-items: flex-start;
  justify-content: center;
  gap: 32px;
  padding: 20px;
  overflow-y: auto;
}

@media (max-width: 768px) {
  .game-body {
    flex-direction: column;
    align-items: center;
    gap: 16px;
    padding: 12px;
  }
}

/* ========================================
   SUDOKU BOARD
   ======================================== */
.board-wrapper {
  position: relative;
  flex-shrink: 0;
  display: flex;
  flex-direction: column;
  align-items: center;
}

/* ===== Hint Explanation Banner ===== */
.hint-explanation-banner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 10px;
  width: 100%;
  max-width: 450px;
  margin-bottom: 10px;
  padding: 8px 12px;
  background: #EFF6FF;
  border: 1px solid #BFDBFE;
  border-radius: var(--radius-sm);
  color: #1E3A8A;
  font-size: 0.82rem;
  line-height: 1.35;
  box-shadow: 0 1px 3px rgba(59, 130, 246, 0.1);
  box-sizing: border-box;
  animation: hintBannerFadeIn 0.25s ease-out;
}

[data-theme="dark"] .hint-explanation-banner {
  background: rgba(30, 58, 138, 0.35);
  border-color: #1E40AF;
  color: #93C5FD;
}

.hint-explanation-banner.hidden {
  display: none !important;
}

.hint-banner-content {
  display: flex;
  align-items: center;
  gap: 8px;
  flex: 1;
  min-width: 0;
}

.hint-banner-icon {
  font-size: 1rem;
  flex-shrink: 0;
}

.hint-banner-text {
  font-weight: 500;
  overflow: hidden;
  text-overflow: ellipsis;
}

.btn-hint-close {
  background: none;
  border: none;
  color: inherit;
  opacity: 0.6;
  font-size: 0.85rem;
  cursor: pointer;
  padding: 2px 6px;
  border-radius: 4px;
  transition: opacity 0.2s ease, background 0.2s ease;
  line-height: 1;
  flex-shrink: 0;
}

.btn-hint-close:hover {
  opacity: 1;
  background: rgba(0, 0, 0, 0.08);
}

@keyframes hintBannerFadeIn {
  from {
    opacity: 0;
    transform: translateY(-6px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

.sudoku-board {
  display: grid;
  grid-template-columns: repeat(9, 1fr);
  grid-template-rows: repeat(9, 1fr);
  width: 450px;
  height: 450px;
  background: var(--surface);
  gap: 0;
  border: 2.5px solid var(--board-major-border);
  border-radius: 4px;
  overflow: hidden;
  box-sizing: border-box;
}

@media (max-width: 768px) {
  .sudoku-board {
    width: min(95vw, 400px);
    height: min(95vw, 400px);
  }
}

/* ===== Cells ===== */
.cell {
  background: var(--surface);
  box-sizing: border-box;
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  position: relative;
  transition: background-color 0.15s ease;
  user-select: none;
  font-size: 1.4rem;
  border-right: 1px solid var(--board-border);
  border-bottom: 1px solid var(--board-border);
}

@media (max-width: 768px) {
  .cell {
    font-size: calc(0.8rem + 1.2vw);
  }
}

/* ===== 3x3 Box Borders (100% continuous & seamless) ===== */
/* Vertical major separators after columns 3 and 6 */
.cell.box-right,
.sudoku-board > .cell:nth-child(9n+3),
.sudoku-board > .cell:nth-child(9n+6) {
  border-right: 2.5px solid var(--board-major-border) !important;
}

/* Horizontal major separators after rows 3 and 6 */
.cell.box-bottom,
.sudoku-board > .cell:nth-child(n+19):nth-child(-n+27),
.sudoku-board > .cell:nth-child(n+46):nth-child(-n+54) {
  border-bottom: 2.5px solid var(--board-major-border) !important;
}

/* Outermost cell boundaries flush against board outer border */
.sudoku-board > .cell:nth-child(9n) {
  border-right: none !important;
}

.sudoku-board > .cell:nth-child(n+73) {
  border-bottom: none !important;
}

/* ===== Cell States ===== */
.cell.selected {
  background: var(--selected) !important;
  box-shadow: inset 0 0 0 2.5px #2563EB;
  z-index: 2;
}

[data-theme="dark"] .cell.selected {
  box-shadow: inset 0 0 0 2.5px #93C5FD;
}

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

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

/* Number Colors & Weights:
   - Given: Semibold (600) black in light mode, bright white in dark mode (thon gọn, thanh thoát hơn)
   - User: Medium (500) vibrant blue in ALL states (dày dặn hơn 400, không bị mỏng)
   - Error: Medium (500) red
*/
.cell.given .cell-value {
  color: var(--cell-given, #0F172A) !important;
  font-weight: 600;
}

.cell.user .cell-value {
  color: var(--cell-user, #1D4ED8) !important;
  font-weight: 500;
}

[data-theme="dark"] .cell.given .cell-value {
  color: var(--cell-given, #F8FAFC) !important;
}

[data-theme="dark"] .cell.user .cell-value {
  color: var(--cell-user, #60A5FA) !important;
}

.cell.error .cell-value {
  color: var(--error, #EF4444) !important;
  font-weight: 500;
}

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

.cell.hint-flash {
  animation: hintGlow 0.8s ease-out;
}

@keyframes hintGlow {
  0% {
    background: #FEF3C7;
  }
  100% {
    background: var(--surface);
  }
}

/* ===== Cell Content ===== */
.cell-value {
  font-size: inherit;
  line-height: 1;
  z-index: 1;
}

.cell-notes {
  position: absolute;
  inset: 2px;
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  grid-template-rows: repeat(3, 1fr);
  z-index: 1;
}

.cell-notes .note {
  font-size: 0.55rem;
  color: var(--text-secondary);
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: 500;
  line-height: 1;
}

@media (max-width: 768px) {
  .cell-notes .note {
    font-size: 0.45rem;
  }
}

.cell-notes .note.empty {
  visibility: hidden;
}

/* Highlight candidate note matching selected/active digit */
.cell-notes .note.note-highlighted {
  background: #3B82F6 !important;
  color: #FFFFFF !important;
  border-radius: 3px;
  font-weight: 700;
  box-shadow: 0 1px 2px rgba(59, 130, 246, 0.4);
}

[data-theme="dark"] .cell-notes .note.note-highlighted {
  background: #2563EB !important;
  color: #FFFFFF !important;
}

/* Conflict flash for manual note placement collision (2s animation: 4 pulses x 0.5s) */
.cell.conflict-flash {
  animation: conflictPulse 0.5s ease-in-out 4;
  z-index: 3;
}

@keyframes conflictPulse {
  0%, 100% {
    background-color: var(--surface);
  }
  50% {
    background-color: #FEE2E2 !important;
    box-shadow: inset 0 0 0 2.5px #EF4444 !important;
  }
}

[data-theme="dark"] .cell.conflict-flash {
  animation: conflictPulseDark 0.5s ease-in-out 4;
  z-index: 3;
}

@keyframes conflictPulseDark {
  0%, 100% {
    background-color: var(--surface);
  }
  50% {
    background-color: rgba(239, 68, 68, 0.4) !important;
    box-shadow: inset 0 0 0 2.5px #F87171 !important;
  }
}

/* ===== Pause Overlay ===== */
.pause-overlay {
  position: absolute;
  inset: 0;
  background: var(--pause-bg);
  backdrop-filter: blur(8px);
  -webkit-backdrop-filter: blur(8px);
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 16px;
  z-index: 10;
  border-radius: 4px;
}

.pause-overlay svg {
  width: 48px;
  height: 48px;
  color: var(--text-secondary);
}

.pause-overlay p {
  font-size: 1.25rem;
  font-weight: 600;
  color: var(--text-secondary);
}

/* ========================================
   CONTROLS PANEL
   ======================================== */
.controls-panel {
  display: flex;
  flex-direction: column;
  gap: 14px;
  width: 320px;
  max-width: 340px;
}

@media (max-width: 768px) {
  .controls-panel {
    min-width: auto;
    width: min(95vw, 400px);
    max-width: 400px;
  }
}

/* ===== Tools Row: Grid 3x2 to display all 6 button labels fully without truncation ===== */
.tools-row {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 8px;
}

.tool-btn {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 4px;
  padding: 8px 4px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  cursor: pointer;
  transition: all 0.2s ease;
  position: relative;
  color: var(--text-secondary);
  font-family: inherit;
  min-height: 54px;
  box-sizing: border-box;
}

.tool-btn:hover {
  background: var(--primary-bg);
  border-color: var(--primary-light);
  color: var(--primary);
}

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

.tool-btn.active {
  background: var(--primary-bg);
  border-color: var(--primary);
  color: var(--primary);
}

.tool-btn#btn-fast-fill.active {
  background: rgba(245, 158, 11, 0.12);
  border-color: #F59E0B;
  color: #D97706;
}

.tool-btn#btn-fast-fill.active svg {
  stroke: #D97706;
  fill: rgba(245, 158, 11, 0.25);
}

.tool-btn#btn-fast-fill.active .badge-off {
  background: #D97706;
  color: #FFFFFF;
}

.tool-btn#btn-auto-notes.active {
  background: rgba(37, 99, 235, 0.12);
  border-color: #2563EB;
  color: #2563EB;
}

.tool-btn#btn-auto-notes.active svg {
  stroke: #2563EB;
}

.tool-btn svg {
  width: 22px;
  height: 22px;
  flex-shrink: 0;
}

.tool-label {
  font-size: 0.72rem;
  font-weight: 500;
  text-align: center;
  line-height: 1.15;
  white-space: normal;
  word-break: keep-all;
  max-width: 100%;
}

/* ===== Tool Badges ===== */
.tool-badge {
  position: absolute;
  top: -4px;
  right: -4px;
  font-size: 0.6rem;
  font-weight: 700;
  padding: 2px 5px;
  border-radius: 50px;
  line-height: 1;
}

.badge-off {
  background: var(--border);
  color: var(--text-secondary);
}

.badge-count {
  background: var(--primary);
  color: #FFFFFF;
}

.tool-btn.active .badge-off {
  background: var(--primary);
  color: #FFFFFF;
}

/* ========================================
   NUMPAD
   ======================================== */
.numpad {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 8px;
}

.num-key {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  padding: 12px 8px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  cursor: pointer;
  transition: all 0.2s ease;
  user-select: none;
  min-height: 56px;
  font-family: inherit;
}

.num-key:hover {
  background: var(--primary-bg);
  border-color: var(--primary-light);
}

.num-key:active {
  transform: scale(0.93);
  background: var(--primary);
  color: #FFFFFF;
}

.num-key:active .num-digit {
  color: #FFFFFF;
}

.num-key:active .num-remaining {
  color: rgba(255, 255, 255, 0.8);
}

.num-key .num-digit {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--primary);
  line-height: 1;
}

.num-key .num-remaining {
  font-size: 0.7rem;
  color: var(--text-secondary);
  margin-top: 2px;
}

.num-key.completed {
  visibility: hidden !important;
  pointer-events: none !important;
  opacity: 0 !important;
}

/* Fast-Fill (Tia chớp) locked digit & dimmed states */
.num-key.locked-digit {
  background: var(--surface);
  border: 2px solid var(--primary);
  box-shadow: 0 0 0 2px var(--primary-light), 0 2px 8px rgba(37, 99, 235, 0.18);
  opacity: 1;
}

.num-key.locked-digit .num-digit {
  color: var(--primary);
}

.num-key.locked-digit .num-remaining {
  color: var(--text-secondary);
}

.num-key.dimmed:not(.completed) {
  opacity: 0.78;
}

.num-key.dimmed:not(.completed):hover {
  opacity: 1;
  border-color: var(--primary-light);
}