:root {
  --bg-color: #f0f4f8;
  --primary-color: #4a90e2;
  --primary-dark: #357abd;
  --dark-text: #2c3e50;
  --border-color: #d1d9e6;
  --thick-border: 3px solid #2c3e50;
  --cell-size: 45px;
  --card-bg: #ffffff;
  --card-shadow: rgba(0, 0, 0, 0.05);
  --cell-bg: #fff;
  --cell-fixed-bg: #f1f3f5;
  --cell-fixed-text: #adb5bd;
  --cell-selected-bg: #e3f2fd;
  --cell-highlight-line: #e8f4fc;
  --cell-highlight-same: #fff3cd;
  --same-number-border: #ffc107;
  --numpad-bg: white;
  --numpad-border: #dee2e6;
  --numpad-shadow: #e0e6ed;
  --numpad-special-bg: #f1f3f5;
  --status-inactive: #7f8c8d;
}

[data-theme="dark"] {
  --bg-color: #1a1a2e;
  --dark-text: #eaeaea;
  --border-color: #3a3a5a;
  --thick-border: 3px solid #6a6a8a;
  --card-bg: #16213e;
  --card-shadow: rgba(0, 0, 0, 0.3);
  --cell-bg: #1e2746;
  --cell-fixed-bg: #252a40;
  --cell-fixed-text: #6a6a8a;
  --cell-selected-bg: #2a3a5a;
  --cell-highlight-line: #232d45;
  --cell-highlight-same: #3d3a20;
  --same-number-border: #b8860b;
  --numpad-bg: #16213e;
  --numpad-border: #3a3a5a;
  --numpad-shadow: #0a0a1e;
  --numpad-special-bg: #252a40;
  --status-inactive: #6a6a8a;
}

body {
  font-family: 'Pretendard', sans-serif;
  background: var(--bg-color);
  display: flex;
  flex-direction: column;
  align-items: center;
  margin: 0;
  padding: 10px;
  touch-action: manipulation;
  color: var(--dark-text);
  transition: background 0.3s, color 0.3s;
}

.topbar {
  width: 100%;
  max-width: 520px;
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 10px;
  flex-wrap: wrap;
  margin-top: 10px;
}

.badge {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 10px 12px;
  border-radius: 12px;
  background: var(--card-bg);
  box-shadow: 0 5px 15px var(--card-shadow);
  color: var(--dark-text);
  font-weight: 700;
}

.smallbtn {
  text-decoration: none;
  background: #4A90E2;
  color: white;
  padding: 10px 14px;
  border-radius: 10px;
  font-weight: bold;
  border: none;
  cursor: pointer;
}

.smallbtn.secondary {
  background: var(--numpad-special-bg);
  color: var(--dark-text);
}

#game-container {
  display: block;
  max-width: 500px;
  width: 100%;
  text-align: center;
}

.controls {
  display: flex;
  justify-content: center;
  align-items: center;
  gap: 10px;
  margin-bottom: 20px;
  background: var(--card-bg);
  padding: 20px;
  border-radius: 18px;
  box-shadow: 0 8px 20px var(--card-shadow);
  flex-wrap: wrap;
}

#difficulty {
  padding: 12px 15px;
  border: 2px solid var(--border-color);
  border-radius: 10px;
  font-size: 1rem;
  font-weight: 600;
  color: var(--dark-text);
  outline: none;
  transition: all 0.2s ease;
  background-color: var(--numpad-special-bg);
}

#difficulty:focus {
  border-color: var(--primary-color);
  background-color: var(--card-bg);
  box-shadow: 0 0 8px rgba(74, 144, 226, 0.2);
}

button#start-btn {
  padding: 12px 25px;
  cursor: pointer;
  border: none;
  border-radius: 10px;
  background: var(--primary-color);
  color: white;
  font-weight: 800;
  font-size: 1rem;
  box-shadow: 0 4px 0 var(--primary-dark);
  transition: 0.1s;
}

button#start-btn:active {
  transform: translateY(3px);
  box-shadow: none;
}

.status-bar {
  display: flex;
  justify-content: space-between;
  margin: 10px 10px;
  font-weight: bold;
  font-size: 1.1rem;
  color: var(--status-inactive);
}

.status-bar.active {
  color: var(--dark-text);
}

#sudoku-grid {
  display: grid;
  grid-template-columns: repeat(9, var(--cell-size));
  grid-template-rows: repeat(9, var(--cell-size));
  border: var(--thick-border);
  margin: 0 auto;
  background: var(--card-bg);
  width: fit-content;
  user-select: none;
  border-radius: 4px;
  overflow: hidden;
  box-shadow: 0 10px 30px var(--card-shadow);
}

.cell {
  width: var(--cell-size);
  height: var(--cell-size);
  border: 0.5px solid var(--border-color);
  box-sizing: border-box;
  position: relative;
  cursor: pointer;
  display: flex;
  justify-content: center;
  align-items: center;
  font-size: 1.5rem;
  font-weight: bold;
  background: var(--cell-bg);
  color: var(--dark-text);
}

.cell:nth-child(3n) {
  border-right: var(--thick-border);
}

.cell:nth-child(9n) {
  border-right: 0.5px solid var(--border-color);
}

.cell:nth-child(n+19):nth-child(-n+27),
.cell:nth-child(n+46):nth-child(-n+54) {
  border-bottom: var(--thick-border);
}

.cell.selected {
  background-color: var(--cell-selected-bg);
  box-shadow: inset 0 0 0 2px var(--primary-color);
  z-index: 5;
}

.cell.fixed {
  background: var(--cell-fixed-bg);
  color: var(--cell-fixed-text);
  cursor: default;
}

/* 같은 행/열/박스 하이라이트 */
.cell.highlight-line {
  background-color: var(--cell-highlight-line);
}

/* 동일 숫자 하이라이트 */
.cell.highlight-same {
  background-color: var(--cell-highlight-same);
  box-shadow: inset 0 0 0 2px var(--same-number-border);
}

/* 선택된 셀은 다른 하이라이트보다 우선 */
.cell.selected.highlight-line,
.cell.selected.highlight-same {
  background-color: var(--cell-selected-bg);
  box-shadow: inset 0 0 0 2px var(--primary-color);
}

.val-span.input-correct {
  color: #2d89ef !important;
}

.val-span.input-wrong {
  color: #ff4d4f !important;
}

.num-pad {
  display: grid;
  grid-template-columns: repeat(5, 1fr);
  gap: 10px;
  margin-top: 20px;
  opacity: 0.2;
  pointer-events: none;
  transition: 0.3s;
}

.num-pad.active {
  opacity: 1;
  pointer-events: auto;
}

.num-btn {
  padding: 16px 0;
  background: var(--numpad-bg);
  color: var(--dark-text) !important;
  border: 1px solid var(--numpad-border);
  border-radius: 12px;
  font-size: 1.4rem;
  font-weight: 800;
  cursor: pointer;
  box-shadow: 0 3px 0 var(--numpad-shadow);
}

.num-btn:active {
  transform: translateY(2px);
  box-shadow: none;
  background: var(--numpad-special-bg);
}

.num-btn.special {
  background: var(--numpad-special-bg);
  font-size: 0.9rem;
  color: var(--status-inactive) !important;
}

.num-btn.memo-active {
  background: #2c3e50 !important;
  color: white !important;
  box-shadow: 0 3px 0 #1a252f;
}

.memo-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  grid-template-rows: repeat(3, 1fr);
  width: 100%;
  height: 100%;
  position: absolute;
  pointer-events: none;
}

.memo-num {
  font-size: 0.65rem;
  color: var(--cell-fixed-text);
  display: flex;
  justify-content: center;
  align-items: center;
}

/* 키보드 힌트 */
.keyboard-hint {
  margin-top: 15px;
  padding: 12px 16px;
  background: var(--card-bg);
  border: 1px dashed var(--border-color);
  border-radius: 10px;
  font-size: 0.85rem;
  color: var(--status-inactive);
  text-align: center;
}

.keyboard-hint strong {
  color: var(--dark-text);
}

/* 커스텀 팝업 모달 */
.popup-overlay {
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, 0.5);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 1000;
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.25s ease;
}

.popup-overlay.show {
  opacity: 1;
  pointer-events: auto;
}

.popup-modal {
  background: var(--card-bg);
  border-radius: 18px;
  padding: 30px 25px;
  max-width: 340px;
  width: 90%;
  box-shadow: 0 15px 40px rgba(0, 0, 0, 0.3);
  text-align: center;
  transform: scale(0.9);
  transition: transform 0.25s ease;
}

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

.popup-icon {
  font-size: 3rem;
  margin-bottom: 15px;
}

.popup-title {
  font-size: 1.4rem;
  font-weight: 900;
  color: var(--dark-text);
  margin-bottom: 12px;
}

.popup-message {
  font-size: 1rem;
  color: var(--dark-text);
  line-height: 1.6;
  margin-bottom: 8px;
  white-space: pre-line;
}

.popup-score-box {
  background: var(--numpad-special-bg);
  border-radius: 12px;
  padding: 15px;
  margin: 15px 0;
}

.popup-score-row {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 6px 0;
  font-weight: 600;
}

.popup-score-row .label {
  color: var(--status-inactive);
  font-size: 0.95rem;
}

.popup-score-row .value {
  color: var(--dark-text);
  font-size: 1.1rem;
  font-weight: 800;
}

.popup-score-row .value.highlight {
  color: var(--primary-color);
}

.popup-score-row .value.new-record {
  color: #27ae60;
}

.popup-btn {
  padding: 14px 30px;
  border: none;
  border-radius: 12px;
  background: var(--primary-color);
  color: white;
  font-weight: 800;
  font-size: 1rem;
  cursor: pointer;
  box-shadow: 0 4px 0 var(--primary-dark);
  transition: 0.1s;
  margin-top: 10px;
}

.popup-btn:active {
  transform: translateY(3px);
  box-shadow: none;
}

.popup-btn.secondary {
  background: var(--numpad-special-bg);
  color: var(--dark-text);
  box-shadow: 0 4px 0 var(--numpad-shadow);
}

.popup-buttons {
  display: flex;
  gap: 10px;
  justify-content: center;
  margin-top: 10px;
}

.popup-sub {
  font-size: 0.85rem;
  color: var(--status-inactive);
  margin-top: 12px;
}

@media (max-width: 500px) {
  :root {
    --cell-size: 10.5vw;
  }

  .controls {
    gap: 8px;
    padding: 15px;
  }

  #user-id {
    width: 90px;
  }
}

/* ===== num-pad: 남은 개수 표시 ===== */
.num-btn[data-num] {
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  gap: 2px;
  line-height: 1;
}

.num-btn[data-num] .num-main {
  font-size: 1.4rem;
  font-weight: 900;
}

.num-btn[data-num] .num-sub {
  font-size: 0.75rem;
  font-weight: 800;
  opacity: 0.6;
}

/* 남은 개수 0이면 "사라지게" (레이아웃 유지하며 안 보이게) */
.num-btn.done {
  visibility: hidden;
  pointer-events: none;
}