/* ===== 数字方块动画 - 童趣卡通风格 ===== */
/* 系统圆体字体栈，无需外部依赖 */
:root {
  --bg: #f0f4ff;
  --card-bg: #ffffff;
  --primary: #6c5ce7;
  --primary-light: #a29bfe;
  --secondary: #fd79a8;
  --accent: #00cec9;
  --text: #2d3436;
  --text-light: #636e72;
  --border: #dfe6e9;
  --shadow: 0 4px 20px rgba(108, 92, 231, 0.15);
  --radius: 20px;
  --radius-sm: 12px;
  --font: 'Nunito', 'Comic Sans MS', 'PingFang SC', 'Microsoft YaHei', cursive, sans-serif;
  --transition: 0.25s cubic-bezier(0.4, 0, 0.2, 1);
}

* { margin: 0; padding: 0; box-sizing: border-box; }

body {
  font-family: var(--font);
  background: linear-gradient(135deg, #e8ecff 0%, #fce4ec 50%, #e0f7fa 100%);
  min-height: 100vh;
  color: var(--text);
  display: flex;
  justify-content: center;
  padding: 16px;
}

.app-wrapper {
  width: 100%;
  max-width: 960px;
  display: flex;
  flex-direction: column;
  gap: 16px;
}

/* ===== Header ===== */
.app-header {
  text-align: center;
  padding: 12px 0 4px;
}
.title {
  font-size: 2.2rem;
  font-weight: 900;
  background: linear-gradient(135deg, #6c5ce7, #fd79a8, #fdcb6e);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  letter-spacing: 2px;
}
.subtitle {
  font-size: 1rem;
  color: var(--text-light);
  font-weight: 600;
  margin-top: 2px;
}

/* ===== Controls Panel ===== */
.controls-panel {
  background: var(--card-bg);
  border-radius: var(--radius);
  padding: 20px 24px;
  box-shadow: var(--shadow);
  display: flex;
  flex-wrap: wrap;
  gap: 16px;
  align-items: flex-end;
}

.control-section {
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.control-label {
  font-size: 0.85rem;
  font-weight: 700;
  color: var(--text-light);
  text-transform: uppercase;
  letter-spacing: 1px;
}

/* Mode toggle */
.mode-toggle {
  display: flex;
  gap: 4px;
  background: #f1f3f9;
  border-radius: var(--radius-sm);
  padding: 4px;
}
.mode-btn {
  border: none;
  background: transparent;
  padding: 8px 20px;
  border-radius: 10px;
  font-family: var(--font);
  font-size: 0.95rem;
  font-weight: 700;
  color: var(--text-light);
  cursor: pointer;
  transition: var(--transition);
}
.mode-btn.active {
  background: var(--primary);
  color: #fff;
  box-shadow: 0 2px 8px rgba(108, 92, 231, 0.4);
}
.mode-btn:hover:not(.active) {
  background: rgba(108, 92, 231, 0.1);
}

/* Expression inputs */
.expression-inputs {
  display: flex;
  align-items: center;
  gap: 8px;
}
.num-input {
  width: 72px;
  padding: 10px 8px;
  border: 3px solid var(--border);
  border-radius: var(--radius-sm);
  font-family: var(--font);
  font-size: 1.2rem;
  font-weight: 800;
  text-align: center;
  color: var(--text);
  background: #fafbff;
  transition: var(--transition);
}
.num-input:focus {
  outline: none;
  border-color: var(--primary);
  box-shadow: 0 0 0 4px rgba(108, 92, 231, 0.15);
}
.num-input.hidden { display: none; }

.op-select {
  padding: 10px 8px;
  border: 3px solid var(--border);
  border-radius: var(--radius-sm);
  font-family: var(--font);
  font-size: 1.3rem;
  font-weight: 800;
  background: #fafbff;
  color: var(--primary);
  cursor: pointer;
  text-align: center;
  min-width: 52px;
  transition: var(--transition);
}
.op-select:focus {
  outline: none;
  border-color: var(--primary);
}
.op-select.hidden { display: none; }

/* Action buttons */
.action-section {
  flex-direction: row;
  align-items: center;
  gap: 10px;
}

.btn-play, .btn-stop {
  padding: 12px 28px;
  border: none;
  border-radius: 30px;
  font-family: var(--font);
  font-size: 1rem;
  font-weight: 800;
  cursor: pointer;
  transition: var(--transition);
  letter-spacing: 1px;
}
.btn-play {
  background: linear-gradient(135deg, #6c5ce7, #a29bfe);
  color: #fff;
  box-shadow: 0 4px 15px rgba(108, 92, 231, 0.4);
}
.btn-play:hover {
  transform: translateY(-2px);
  box-shadow: 0 6px 20px rgba(108, 92, 231, 0.5);
}
.btn-play:active { transform: translateY(0); }
.btn-play:disabled {
  opacity: 0.5;
  cursor: not-allowed;
  transform: none;
}

.btn-stop {
  background: #fab1a0;
  color: #fff;
  box-shadow: 0 4px 15px rgba(250, 177, 160, 0.4);
}
.btn-stop:hover:not(:disabled) {
  transform: translateY(-2px);
  box-shadow: 0 6px 20px rgba(250, 177, 160, 0.5);
}
.btn-stop:disabled {
  opacity: 0.4;
  cursor: not-allowed;
}

.speed-control {
  display: flex;
  align-items: center;
  gap: 6px;
}
.speed-control label {
  font-size: 0.8rem;
  font-weight: 700;
  color: var(--text-light);
}
.speed-control input[type=range] {
  width: 80px;
  accent-color: var(--primary);
}
#speedLabel {
  font-size: 0.85rem;
  font-weight: 700;
  color: var(--primary);
  min-width: 36px;
}

/* Background buttons */
.bg-buttons {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
}
.bg-btn {
  padding: 7px 14px;
  border: 2px solid var(--border);
  border-radius: 20px;
  background: #fff;
  font-family: var(--font);
  font-size: 0.85rem;
  font-weight: 700;
  color: var(--text-light);
  cursor: pointer;
  transition: var(--transition);
}
.bg-btn:hover {
  border-color: var(--primary-light);
  color: var(--primary);
}
.bg-btn.active {
  border-color: var(--primary);
  background: rgba(108, 92, 231, 0.08);
  color: var(--primary);
}
.bg-random-btn {
  background: linear-gradient(135deg, #ffeaa7, #fab1a0);
  border-color: #ffeaa7;
  color: #d63031;
}
.bg-random-btn:hover {
  border-color: #fab1a0;
  transform: scale(1.05);
}

/* ===== Canvas ===== */
.canvas-wrapper {
  position: relative;
  background: var(--card-bg);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  overflow: hidden;
  aspect-ratio: 16 / 9;
}
#mainCanvas {
  width: 100%;
  height: 100%;
  display: block;
}
.step-overlay {
  position: absolute;
  bottom: 16px;
  left: 50%;
  transform: translateX(-50%);
  background: rgba(255, 255, 255, 0.92);
  backdrop-filter: blur(8px);
  border-radius: 30px;
  padding: 10px 28px;
  text-align: center;
  box-shadow: 0 4px 15px rgba(0, 0, 0, 0.12);
  pointer-events: none;
}
.step-text {
  font-size: 1.1rem;
  font-weight: 800;
  color: var(--primary);
}
.step-sub {
  display: block;
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--text-light);
  margin-top: 2px;
}

/* Result bar */
.result-bar {
  background: var(--card-bg);
  border-radius: var(--radius);
  padding: 16px 24px;
  box-shadow: var(--shadow);
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
}
.result-label {
  font-size: 1.1rem;
  font-weight: 700;
  color: var(--text-light);
}
.result-value {
  font-size: 1.8rem;
  font-weight: 900;
  color: var(--primary);
  transition: var(--transition);
}

/* ===== Responsive ===== */
@media (max-width: 640px) {
  .title { font-size: 1.5rem; }
  .controls-panel { padding: 14px 16px; gap: 12px; }
  .num-input { width: 56px; padding: 8px 4px; font-size: 1rem; }
  .expression-inputs { gap: 4px; }
  .btn-play, .btn-stop { padding: 10px 20px; font-size: 0.9rem; }
  .bg-btn { padding: 5px 10px; font-size: 0.75rem; }
  .step-text { font-size: 0.95rem; }
}