/* ===== Reset & Base ===== */
*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

:root {
  --bg: #f5f7fa;
  --bg-panel: #ffffff;
  --text: #1a1a2e;
  --text-muted: #6b7280;
  --border: #e2e8f0;
  --accent: #6366f1;
  --accent-light: #a5b4fc;
  --canvas-bg: #f8fafc;
  --curve-color: #6366f1;
  --control-color: #f43f5e;
  --grid-color: #e2e8f0;
  --shadow: 0 2px 12px rgba(0,0,0,0.06);
  --code-bg: #1e1e2e;
  --code-text: #cdd6f4;
  --ball-color: #6366f1;
  --compare-ball: #f59e0b;
  --track-bg: #e2e8f0;
  --preset-bg: #f1f5f9;
  --preset-hover: #e0e7ff;
  --preset-active: #6366f1;
  --preset-active-text: #ffffff;
  --copy-ok: #10b981;
}

[data-theme="dark"] {
  --bg: #0f172a;
  --bg-panel: #1e293b;
  --text: #e2e8f0;
  --text-muted: #94a3b8;
  --border: #334155;
  --canvas-bg: #1e293b;
  --grid-color: #334155;
  --shadow: 0 2px 12px rgba(0,0,0,0.3);
  --track-bg: #334155;
  --preset-bg: #334155;
  --preset-hover: #4338ca;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Noto Sans SC", sans-serif;
  background: var(--bg);
  color: var(--text);
  min-height: 100vh;
  transition: background 0.3s, color 0.3s;
}

/* ===== Header ===== */
.header {
  background: var(--bg-panel);
  border-bottom: 1px solid var(--border);
  padding: 14px 24px;
  box-shadow: var(--shadow);
  position: sticky;
  top: 0;
  z-index: 100;
}

.header-inner {
  max-width: 1200px;
  margin: 0 auto;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.logo {
  font-size: 1.25rem;
  font-weight: 700;
}

.theme-toggle {
  background: none;
  border: 2px solid var(--border);
  border-radius: 8px;
  padding: 6px 10px;
  font-size: 1.1rem;
  cursor: pointer;
  transition: border-color 0.2s;
}

.theme-toggle:hover {
  border-color: var(--accent);
}

/* ===== Main Layout ===== */
.main {
  max-width: 1200px;
  margin: 24px auto;
  padding: 0 24px;
}

.editor-section {
  display: flex;
  gap: 24px;
  flex-wrap: wrap;
}

.panel {
  background: var(--bg-panel);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 20px;
  box-shadow: var(--shadow);
  flex: 1;
  min-width: 340px;
}

.panel-title {
  font-size: 1rem;
  font-weight: 600;
  margin-bottom: 12px;
  color: var(--text);
}

/* ===== Canvas ===== */
.canvas-wrap {
  position: relative;
  width: 100%;
  max-width: 400px;
  margin: 0 auto;
  aspect-ratio: 1;
  background: var(--canvas-bg);
  border: 1px solid var(--border);
  border-radius: 8px;
  overflow: hidden;
}

#curveCanvas {
  width: 100%;
  height: 100%;
  display: block;
  cursor: crosshair;
}

/* ===== Curve Info ===== */
.curve-info {
  display: flex;
  flex-wrap: wrap;
  gap: 8px 16px;
  margin-top: 12px;
  font-size: 0.85rem;
}

.info-label {
  color: var(--text-muted);
  font-weight: 500;
}

.info-value {
  color: var(--accent);
  font-family: "SF Mono", "Fira Code", monospace;
  font-weight: 600;
}

/* ===== Presets ===== */
.presets-grid {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
}

.preset-btn {
  padding: 5px 10px;
  font-size: 0.78rem;
  border: 1px solid var(--border);
  border-radius: 6px;
  background: var(--preset-bg);
  color: var(--text);
  cursor: pointer;
  transition: all 0.15s;
  white-space: nowrap;
}

.preset-btn:hover {
  background: var(--preset-hover);
  border-color: var(--accent);
}

.preset-btn.active {
  background: var(--preset-active);
  color: var(--preset-active-text);
  border-color: var(--preset-active);
}

/* ===== Code Output ===== */
.code-output {
  display: flex;
  align-items: center;
  gap: 8px;
  background: var(--code-bg);
  color: var(--code-text);
  padding: 10px 14px;
  border-radius: 8px;
  font-family: "SF Mono", "Fira Code", monospace;
  font-size: 0.85rem;
  word-break: break-all;
}

.code-output code {
  flex: 1;
}

.copy-btn {
  background: none;
  border: none;
  font-size: 1.1rem;
  cursor: pointer;
  padding: 4px;
  border-radius: 4px;
  transition: background 0.15s;
}

.copy-btn:hover {
  background: rgba(255,255,255,0.1);
}

.copy-feedback {
  font-size: 0.8rem;
  color: var(--copy-ok);
  opacity: 0;
  transition: opacity 0.3s;
  margin-top: 4px;
  display: inline-block;
}

.copy-feedback.show {
  opacity: 1;
}

/* ===== Duration ===== */
.duration-control {
  display: flex;
  align-items: center;
  gap: 10px;
  margin-bottom: 10px;
  font-size: 0.9rem;
}

.duration-control label {
  color: var(--text-muted);
  font-weight: 500;
}

.duration-control input[type="range"] {
  flex: 1;
  accent-color: var(--accent);
}

.duration-control span {
  font-family: "SF Mono", "Fira Code", monospace;
  color: var(--accent);
  font-weight: 600;
  min-width: 40px;
}

/* ===== Preview ===== */
.preview-area {
  margin-bottom: 8px;
}

.preview-track {
  height: 44px;
  background: var(--track-bg);
  border-radius: 22px;
  position: relative;
  overflow: hidden;
}

.preview-ball {
  width: 36px;
  height: 36px;
  border-radius: 50%;
  background: var(--ball-color);
  position: absolute;
  top: 4px;
  left: 4px;
  transition: none;
}

.preview-ball.animate {
  transition-property: left;
  transition-timing-function: var(--current-bezier, cubic-bezier(0.25,0.1,0.25,1));
  transition-duration: var(--anim-duration, 1s);
  left: calc(100% - 40px);
}

.compare-ball {
  background: var(--compare-ball);
}

.compare-area {
  position: relative;
}

.compare-label {
  font-size: 0.75rem;
  color: var(--compare-ball);
  font-weight: 600;
  margin-top: 4px;
  display: block;
}

.play-btn {
  margin-top: 8px;
  padding: 8px 24px;
  background: var(--accent);
  color: #fff;
  border: none;
  border-radius: 8px;
  font-size: 0.9rem;
  font-weight: 600;
  cursor: pointer;
  transition: opacity 0.15s;
}

.play-btn:hover {
  opacity: 0.85;
}

/* ===== Compare ===== */
.compare-controls {
  display: flex;
  align-items: center;
  gap: 12px;
  margin-bottom: 8px;
  font-size: 0.88rem;
}

.compare-controls label {
  display: flex;
  align-items: center;
  gap: 6px;
  cursor: pointer;
  color: var(--text-muted);
}

.compare-controls input[type="checkbox"] {
  accent-color: var(--accent);
}

.compare-controls select {
  padding: 4px 8px;
  border: 1px solid var(--border);
  border-radius: 6px;
  background: var(--bg-panel);
  color: var(--text);
  font-size: 0.85rem;
}

/* ===== Footer ===== */
.footer {
  text-align: center;
  padding: 20px;
  color: var(--text-muted);
  font-size: 0.82rem;
  border-top: 1px solid var(--border);
  margin-top: 32px;
}

.footer a {
  color: var(--accent);
  text-decoration: none;
}

.footer a:hover {
  text-decoration: underline;
}

/* ===== Responsive ===== */
@media (max-width: 768px) {
  .editor-section {
    flex-direction: column;
  }
  .panel {
    min-width: auto;
  }
  .canvas-wrap {
    max-width: 320px;
  }
}