/* ===== DESIGN TOKENS ===== */
:root {
  --bg-primary: #0a0a0f;
  --bg-secondary: #12121a;
  --bg-card: rgba(20, 20, 35, 0.7);
  --bg-glass: rgba(255, 255, 255, 0.04);
  --border-glass: rgba(255, 255, 255, 0.08);
  --border-glow: rgba(139, 92, 246, 0.3);

  --text-primary: #e8e8f0;
  --text-secondary: #8888a0;
  --text-muted: #555570;

  --accent-purple: #8b5cf6;
  --accent-cyan: #06b6d4;
  --accent-pink: #ec4899;
  --accent-green: #10b981;
  --accent-orange: #f59e0b;

  --gradient-primary: linear-gradient(135deg, #8b5cf6, #06b6d4);
  --gradient-warm: linear-gradient(135deg, #ec4899, #f59e0b);
  --gradient-bg: linear-gradient(180deg, #0a0a0f 0%, #0f0f1a 50%, #0a0a0f 100%);

  --shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.3);
  --shadow-md: 0 4px 20px rgba(0, 0, 0, 0.4);
  --shadow-lg: 0 8px 40px rgba(0, 0, 0, 0.5);
  --shadow-glow: 0 0 30px rgba(139, 92, 246, 0.15);

  --radius-sm: 8px;
  --radius-md: 12px;
  --radius-lg: 16px;
  --radius-xl: 24px;

  --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  --font-mono: 'JetBrains Mono', 'Fira Code', 'Consolas', monospace;

  --transition-fast: 150ms cubic-bezier(0.4, 0, 0.2, 1);
  --transition-normal: 250ms cubic-bezier(0.4, 0, 0.2, 1);
  --transition-slow: 400ms cubic-bezier(0.4, 0, 0.2, 1);
}

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

html {
  font-size: 16px;
  scroll-behavior: smooth;
}

body {
  font-family: var(--font-sans);
  background: var(--bg-primary);
  color: var(--text-primary);
  min-height: 100vh;
  overflow-x: hidden;
  line-height: 1.6;
}

/* ===== BACKGROUND EFFECTS ===== */
body::before {
  content: '';
  position: fixed;
  inset: 0;
  background:
    radial-gradient(ellipse 600px 400px at 20% 20%, rgba(139, 92, 246, 0.08), transparent),
    radial-gradient(ellipse 500px 350px at 80% 80%, rgba(6, 182, 212, 0.06), transparent),
    radial-gradient(ellipse 400px 300px at 50% 50%, rgba(236, 72, 153, 0.04), transparent);
  pointer-events: none;
  z-index: 0;
}

/* ===== SCROLLBAR ===== */
::-webkit-scrollbar {
  width: 6px;
}
::-webkit-scrollbar-track {
  background: transparent;
}
::-webkit-scrollbar-thumb {
  background: rgba(139, 92, 246, 0.3);
  border-radius: 3px;
}
::-webkit-scrollbar-thumb:hover {
  background: rgba(139, 92, 246, 0.5);
}

/* ===== LAYOUT ===== */
#app {
  position: relative;
  z-index: 1;
  max-width: 1440px;
  margin: 0 auto;
  padding: 24px;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  gap: 24px;
}

/* ===== HEADER ===== */
.header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 16px 24px;
  background: var(--bg-card);
  backdrop-filter: blur(20px);
  border: 1px solid var(--border-glass);
  border-radius: var(--radius-lg);
}

.header__brand {
  display: flex;
  align-items: center;
  gap: 14px;
}

.header__icon {
  width: 42px;
  height: 42px;
  background: var(--gradient-primary);
  border-radius: var(--radius-md);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 22px;
  box-shadow: var(--shadow-glow);
}

.header__title {
  font-size: 1.35rem;
  font-weight: 700;
  background: var(--gradient-primary);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  letter-spacing: -0.02em;
}

.header__subtitle {
  font-size: 0.8rem;
  color: var(--text-secondary);
  margin-top: -2px;
}

.header__status {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 0.82rem;
  color: var(--text-secondary);
  padding: 6px 14px;
  background: var(--bg-glass);
  border: 1px solid var(--border-glass);
  border-radius: var(--radius-sm);
}

.header__status-dot {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: var(--accent-orange);
  animation: pulse-dot 2s ease-in-out infinite;
}

.header__status-dot.ready {
  background: var(--accent-green);
  animation: none;
}

@keyframes pulse-dot {
  0%, 100% { opacity: 1; transform: scale(1); }
  50% { opacity: 0.5; transform: scale(0.8); }
}

/* ===== MAIN GRID ===== */
.main-grid {
  display: grid;
  grid-template-columns: 340px 1fr;
  gap: 24px;
  flex: 1;
}

/* ===== GLASS CARD ===== */
.card {
  background: var(--bg-card);
  backdrop-filter: blur(20px);
  border: 1px solid var(--border-glass);
  border-radius: var(--radius-lg);
  padding: 24px;
  transition: border-color var(--transition-normal);
}

.card:hover {
  border-color: rgba(255, 255, 255, 0.12);
}

.card__title {
  font-size: 0.78rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--text-secondary);
  margin-bottom: 16px;
  display: flex;
  align-items: center;
  gap: 8px;
}

.card__title-icon {
  font-size: 1rem;
}

/* ===== LEFT PANEL ===== */
.panel-left {
  display: flex;
  flex-direction: column;
  gap: 20px;
}

/* ===== UPLOAD ZONE ===== */
.upload-zone {
  position: relative;
  border: 2px dashed rgba(139, 92, 246, 0.25);
  border-radius: var(--radius-lg);
  padding: 32px 20px;
  text-align: center;
  cursor: pointer;
  transition: all var(--transition-normal);
  overflow: hidden;
  min-height: 180px;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 12px;
}

.upload-zone::before {
  content: '';
  position: absolute;
  inset: 0;
  background: linear-gradient(135deg, rgba(139, 92, 246, 0.03), rgba(6, 182, 212, 0.03));
  opacity: 0;
  transition: opacity var(--transition-normal);
}

.upload-zone:hover::before,
.upload-zone.dragover::before {
  opacity: 1;
}

.upload-zone:hover,
.upload-zone.dragover {
  border-color: var(--accent-purple);
  box-shadow: var(--shadow-glow);
}

.upload-zone.dragover {
  transform: scale(1.01);
}

.upload-zone.has-image {
  padding: 12px;
  border-color: var(--accent-green);
}

.upload-zone__icon {
  font-size: 2.5rem;
  opacity: 0.6;
  transition: transform var(--transition-normal);
}

.upload-zone:hover .upload-zone__icon {
  transform: translateY(-4px);
}

.upload-zone__text {
  font-size: 0.9rem;
  color: var(--text-secondary);
}

.upload-zone__hint {
  font-size: 0.75rem;
  color: var(--text-muted);
}

.upload-zone__preview {
  width: 100%;
  max-height: 200px;
  object-fit: contain;
  border-radius: var(--radius-sm);
  display: none;
}

.upload-zone.has-image .upload-zone__preview {
  display: block;
}

.upload-zone.has-image .upload-zone__icon,
.upload-zone.has-image .upload-zone__text,
.upload-zone.has-image .upload-zone__hint {
  display: none;
}

#file-input {
  display: none;
}

/* ===== SLIDER SECTION ===== */
.slider-section {
  display: flex;
  flex-direction: column;
  gap: 14px;
}

.slider-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.slider-value {
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--accent-purple);
  font-family: var(--font-mono);
}

.slider-container {
  position: relative;
}

.slider-track-bg {
  position: absolute;
  top: 50%;
  left: 0;
  right: 0;
  height: 6px;
  transform: translateY(-50%);
  border-radius: 3px;
  background: linear-gradient(90deg,
    var(--accent-cyan) 0%, var(--accent-cyan) 33%,
    var(--accent-purple) 33%, var(--accent-purple) 66%,
    var(--accent-pink) 66%, var(--accent-pink) 100%
  );
  opacity: 0.2;
  pointer-events: none;
}

input[type="range"] {
  -webkit-appearance: none;
  appearance: none;
  width: 100%;
  height: 6px;
  background: transparent;
  border-radius: 3px;
  outline: none;
  position: relative;
  z-index: 1;
}

input[type="range"]::-webkit-slider-runnable-track {
  height: 6px;
  border-radius: 3px;
  background: transparent;
}

input[type="range"]::-webkit-slider-thumb {
  -webkit-appearance: none;
  appearance: none;
  width: 22px;
  height: 22px;
  border-radius: 50%;
  background: var(--accent-purple);
  border: 3px solid var(--bg-primary);
  cursor: pointer;
  box-shadow: 0 0 12px rgba(139, 92, 246, 0.4);
  margin-top: -8px;
  transition: transform var(--transition-fast), box-shadow var(--transition-fast);
}

input[type="range"]::-webkit-slider-thumb:hover {
  transform: scale(1.15);
  box-shadow: 0 0 20px rgba(139, 92, 246, 0.6);
}

input[type="range"]::-moz-range-thumb {
  width: 22px;
  height: 22px;
  border-radius: 50%;
  background: var(--accent-purple);
  border: 3px solid var(--bg-primary);
  cursor: pointer;
  box-shadow: 0 0 12px rgba(139, 92, 246, 0.4);
}

.slider-labels {
  display: flex;
  justify-content: space-between;
  margin-top: 6px;
}

.slider-label {
  font-size: 0.7rem;
  color: var(--text-muted);
  display: flex;
  align-items: center;
  gap: 4px;
  transition: color var(--transition-fast);
}

.slider-label.active {
  color: var(--text-primary);
}

.slider-label__dot {
  width: 6px;
  height: 6px;
  border-radius: 50%;
}

.slider-label:nth-child(1) .slider-label__dot { background: var(--accent-cyan); }
.slider-label:nth-child(2) .slider-label__dot { background: var(--accent-purple); }
.slider-label:nth-child(3) .slider-label__dot { background: var(--accent-pink); }

/* ===== PROCESS BUTTON ===== */
.btn-process {
  width: 100%;
  padding: 14px 20px;
  border: none;
  border-radius: var(--radius-md);
  background: var(--gradient-primary);
  color: white;
  font-family: var(--font-sans);
  font-size: 0.95rem;
  font-weight: 600;
  cursor: pointer;
  transition: all var(--transition-normal);
  position: relative;
  overflow: hidden;
  letter-spacing: 0.02em;
}

.btn-process::before {
  content: '';
  position: absolute;
  inset: 0;
  background: linear-gradient(135deg, rgba(255,255,255,0.15), transparent);
  opacity: 0;
  transition: opacity var(--transition-fast);
}

.btn-process:hover:not(:disabled)::before {
  opacity: 1;
}

.btn-process:hover:not(:disabled) {
  transform: translateY(-1px);
  box-shadow: 0 6px 24px rgba(139, 92, 246, 0.35);
}

.btn-process:active:not(:disabled) {
  transform: translateY(0);
}

.btn-process:disabled {
  opacity: 0.4;
  cursor: not-allowed;
}

.btn-process.processing {
  background: var(--bg-glass);
  border: 1px solid var(--border-glow);
}

/* ===== PROGRESS ===== */
.progress-section {
  display: none;
}

.progress-section.visible {
  display: block;
}

.progress-bar-track {
  width: 100%;
  height: 4px;
  background: var(--bg-glass);
  border-radius: 2px;
  overflow: hidden;
  margin-bottom: 8px;
}

.progress-bar-fill {
  height: 100%;
  background: var(--gradient-primary);
  border-radius: 2px;
  width: 0%;
  transition: width var(--transition-normal);
}

.progress-text {
  font-size: 0.78rem;
  color: var(--text-secondary);
  text-align: center;
}

/* ===== STATS ===== */
.stats-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 10px;
}

.stat-item {
  padding: 12px;
  background: var(--bg-glass);
  border: 1px solid var(--border-glass);
  border-radius: var(--radius-sm);
  text-align: center;
}

.stat-item__value {
  font-size: 1.3rem;
  font-weight: 700;
  font-family: var(--font-mono);
  background: var(--gradient-primary);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.stat-item__label {
  font-size: 0.7rem;
  color: var(--text-muted);
  margin-top: 2px;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

/* ===== RIGHT PANEL ===== */
.panel-right {
  display: flex;
  flex-direction: column;
  gap: 20px;
  min-width: 0;
}

/* ===== VIEW TABS ===== */
.view-tabs {
  display: flex;
  gap: 4px;
  padding: 4px;
  background: var(--bg-glass);
  border-radius: var(--radius-sm);
  width: fit-content;
}

.view-tab {
  padding: 8px 18px;
  border: none;
  background: transparent;
  color: var(--text-secondary);
  font-family: var(--font-sans);
  font-size: 0.82rem;
  font-weight: 500;
  border-radius: 6px;
  cursor: pointer;
  transition: all var(--transition-fast);
}

.view-tab:hover {
  color: var(--text-primary);
}

.view-tab.active {
  background: var(--accent-purple);
  color: white;
  box-shadow: 0 2px 8px rgba(139, 92, 246, 0.3);
}

/* ===== PREVIEW CANVAS ===== */
.preview-container {
  position: relative;
  background: var(--bg-secondary);
  border: 1px solid var(--border-glass);
  border-radius: var(--radius-lg);
  overflow: hidden;
  min-height: 400px;
  min-width: 0;
  display: flex;
  align-items: center;
  justify-content: center;
}

.preview-container canvas {
  max-width: 100%;
  max-height: 500px;
  display: block;
  object-fit: contain;
}

.preview-placeholder {
  text-align: center;
  color: var(--text-muted);
  padding: 40px;
}

.preview-placeholder__icon {
  font-size: 3rem;
  margin-bottom: 12px;
  opacity: 0.4;
}

.preview-placeholder__text {
  font-size: 0.9rem;
}

/* Desmos container */
#desmos-container {
  width: 100%;
  height: 500px;
  display: none;
  border-radius: var(--radius-md);
  overflow: hidden;
}

#desmos-container.visible {
  display: block;
}

/* ===== EQUATIONS PANEL ===== */
.equations-panel {
  max-height: 350px;
  overflow-y: auto;
  display: flex;
  flex-direction: column;
  gap: 6px;
}

.equation-item {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 10px 14px;
  background: var(--bg-glass);
  border: 1px solid var(--border-glass);
  border-radius: var(--radius-sm);
  font-family: var(--font-mono);
  font-size: 0.75rem;
  color: var(--text-secondary);
  transition: all var(--transition-fast);
  cursor: default;
}

.equation-item:hover {
  border-color: var(--border-glow);
  background: rgba(139, 92, 246, 0.05);
}

.equation-item__index {
  font-size: 0.65rem;
  color: var(--text-muted);
  min-width: 28px;
  text-align: right;
}

.equation-item__text {
  flex: 1;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.equation-item__copy {
  padding: 4px 8px;
  border: none;
  background: rgba(139, 92, 246, 0.15);
  color: var(--accent-purple);
  border-radius: 4px;
  font-size: 0.7rem;
  cursor: pointer;
  opacity: 0;
  transition: opacity var(--transition-fast);
  font-family: var(--font-sans);
}

.equation-item:hover .equation-item__copy {
  opacity: 1;
}

.equation-item__copy:hover {
  background: rgba(139, 92, 246, 0.3);
}

.equations-empty {
  text-align: center;
  padding: 30px;
  color: var(--text-muted);
  font-size: 0.85rem;
}

/* ===== EXPORT BUTTONS ===== */
.export-actions {
  display: flex;
  gap: 10px;
  flex-wrap: wrap;
}

.btn-export {
  flex: 1;
  min-width: 120px;
  padding: 10px 16px;
  border: 1px solid var(--border-glass);
  border-radius: var(--radius-sm);
  background: var(--bg-glass);
  color: var(--text-secondary);
  font-family: var(--font-sans);
  font-size: 0.82rem;
  font-weight: 500;
  cursor: pointer;
  transition: all var(--transition-fast);
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 6px;
}

.btn-export:hover:not(:disabled) {
  border-color: var(--accent-purple);
  color: var(--text-primary);
  background: rgba(139, 92, 246, 0.08);
}

.btn-export:disabled {
  opacity: 0.3;
  cursor: not-allowed;
}

/* ===== TOAST ===== */
.toast {
  position: fixed;
  bottom: 30px;
  left: 50%;
  transform: translateX(-50%) translateY(100px);
  padding: 12px 24px;
  background: var(--bg-card);
  backdrop-filter: blur(20px);
  border: 1px solid var(--accent-green);
  border-radius: var(--radius-md);
  color: var(--accent-green);
  font-size: 0.85rem;
  font-weight: 500;
  z-index: 100;
  opacity: 0;
  transition: all var(--transition-slow);
  pointer-events: none;
  box-shadow: 0 4px 20px rgba(16, 185, 129, 0.2);
}

.toast.visible {
  transform: translateX(-50%) translateY(0);
  opacity: 1;
}

/* ===== LOADING OVERLAY ===== */
.loading-overlay {
  position: fixed;
  inset: 0;
  background: rgba(10, 10, 15, 0.85);
  backdrop-filter: blur(8px);
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 20px;
  z-index: 200;
  transition: opacity var(--transition-slow);
}

.loading-overlay.hidden {
  opacity: 0;
  pointer-events: none;
}

.loading-spinner {
  width: 48px;
  height: 48px;
  border: 3px solid rgba(139, 92, 246, 0.15);
  border-top-color: var(--accent-purple);
  border-radius: 50%;
  animation: spin 0.8s linear infinite;
}

@keyframes spin {
  to { transform: rotate(360deg); }
}

.loading-text {
  color: var(--text-secondary);
  font-size: 0.9rem;
}

/* ===== MODE SELECTOR ===== */
.mode-selector {
  display: flex;
  gap: 4px;
  padding: 4px;
  background: var(--bg-glass);
  border: 1px solid var(--border-glass);
  border-radius: var(--radius-sm);
}

.mode-btn {
  flex: 1;
  padding: 8px 14px;
  border: none;
  background: transparent;
  color: var(--text-secondary);
  font-family: var(--font-sans);
  font-size: 0.8rem;
  font-weight: 500;
  border-radius: 6px;
  cursor: pointer;
  transition: all var(--transition-fast);
  white-space: nowrap;
}

.mode-btn:hover {
  color: var(--text-primary);
}

.mode-btn.active {
  background: var(--accent-purple);
  color: white;
  box-shadow: 0 2px 8px rgba(139, 92, 246, 0.3);
}

/* Canvas crosshair cursor for regression mode */
.preview-container.regression-mode canvas#preview-canvas {
  cursor: crosshair;
}

/* ===== RESPONSIVE ===== */
@media (max-width: 900px) {
  .main-grid {
    grid-template-columns: 1fr;
  }

  .header {
    flex-direction: column;
    gap: 12px;
    text-align: center;
  }

  #app {
    padding: 16px;
  }

  #desmos-container {
    height: 350px;
  }
}

@media (max-width: 500px) {
  .stats-grid {
    grid-template-columns: 1fr;
  }

  .export-actions {
    flex-direction: column;
  }
}