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

/* ===== Light Theme (default) ===== */
:root {
  --bg-primary: #f5f5f9;
  --bg-secondary: #ffffff;
  --bg-card: rgba(0, 0, 0, 0.02);
  --bg-glass: rgba(255, 255, 255, 0.7);
  --bg-hover: rgba(0, 0, 0, 0.04);
  --border-glass: rgba(0, 0, 0, 0.08);
  --border-hover: rgba(0, 0, 0, 0.15);
  --text-primary: #1a1a2e;
  --text-secondary: #555568;
  --text-muted: #8888a0;
  --accent-rgb: 100, 80, 240;
  --accent: #6450f0;
  --accent-light: #8070ff;
  --accent-soft: rgba(var(--accent-rgb), 0.1);
  --accent-glow: rgba(var(--accent-rgb), 0.2);
  --danger-rgb: 230, 70, 70;
  --danger: #e64646;
  --success-rgb: 34, 180, 90;
  --success: #22b45a;
  --radius: 20px;
  --radius-md: 14px;
  --radius-sm: 10px;
  --shadow: 0 4px 24px rgba(0, 0, 0, 0.08);
  --shadow-lg: 0 12px 40px rgba(0, 0, 0, 0.12);
  --transition: 0.25s cubic-bezier(0.4, 0, 0.2, 1);
  --transition-slow: 0.4s cubic-bezier(0.4, 0, 0.2, 1);
  --card-info-bg: rgba(0, 0, 0, 0.04);
  --card-info-border: rgba(0, 0, 0, 0.06);
  --progress-track: rgba(0, 0, 0, 0.06);
  --overlay-bg: rgba(255, 255, 255, 0.8);
  --scrollbar-thumb: rgba(0, 0, 0, 0.12);
  --scrollbar-thumb-hover: rgba(0, 0, 0, 0.22);
  --select-arrow: %239a9ab0;
  --h1-gradient-start: var(--accent);
  --h1-gradient-mid: var(--accent-light);
  --h1-gradient-end: #a78bfa;
  --remove-btn-bg: rgba(0, 0, 0, 0.5);
  color-scheme: light;
}

/* ===== Dark Theme ===== */
[data-theme="dark"] {
  --bg-primary: #0a0a14;
  --bg-secondary: #12121f;
  --bg-card: rgba(255, 255, 255, 0.03);
  --bg-glass: rgba(255, 255, 255, 0.05);
  --bg-hover: rgba(255, 255, 255, 0.08);
  --border-glass: rgba(255, 255, 255, 0.07);
  --border-hover: rgba(255, 255, 255, 0.14);
  --text-primary: #ececf4;
  --text-secondary: #a0a0b8;
  --text-muted: #6b6b82;
  --accent-rgb: 124, 108, 255;
  --accent: #7c6cff;
  --accent-light: #9b8fff;
  --accent-soft: rgba(var(--accent-rgb), 0.12);
  --accent-glow: rgba(var(--accent-rgb), 0.25);
  --danger-rgb: 255, 107, 107;
  --danger: #ff6b6b;
  --success-rgb: 74, 222, 128;
  --success: #4ade80;
  --shadow: 0 8px 32px rgba(0, 0, 0, 0.3);
  --shadow-lg: 0 16px 48px rgba(0, 0, 0, 0.4);
  --card-info-bg: rgba(0, 0, 0, 0.2);
  --card-info-border: rgba(255, 255, 255, 0.04);
  --progress-track: rgba(255, 255, 255, 0.06);
  --overlay-bg: rgba(0, 0, 0, 0.75);
  --scrollbar-thumb: rgba(255, 255, 255, 0.1);
  --scrollbar-thumb-hover: rgba(255, 255, 255, 0.18);
  --select-arrow: %239a9ab0;
  --h1-gradient-start: #fff;
  --h1-gradient-mid: var(--accent-light);
  --h1-gradient-end: var(--accent);
  --remove-btn-bg: rgba(0, 0, 0, 0.55);
  color-scheme: dark;
}

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

body {
  font-family: 'Inter', 'Noto Sans JP', -apple-system, BlinkMacSystemFont, sans-serif;
  background: var(--bg-primary);
  color: var(--text-primary);
  min-height: 100vh;
  line-height: 1.6;
  overflow-x: hidden;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  transition: background var(--transition-slow), color var(--transition-slow);
}

/* Background decoration */
body::before {
  content: '';
  position: fixed;
  top: -10%;
  left: -10%;
  width: 120%;
  height: 120%;
  background:
    radial-gradient(ellipse at 15% 30%, rgba(var(--accent-rgb), 0.07) 0%, transparent 50%),
    radial-gradient(ellipse at 85% 60%, rgba(var(--accent-rgb), 0.04) 0%, transparent 50%),
    radial-gradient(ellipse at 50% 90%, rgba(var(--accent-rgb), 0.03) 0%, transparent 40%);
  z-index: -1;
  animation: bgShift 25s ease-in-out infinite alternate;
}

@keyframes bgShift {
  0%   { transform: translate(0, 0) rotate(0deg); }
  100% { transform: translate(-3%, -2%) rotate(1deg); }
}

/* ===== Layout ===== */
.container {
  max-width: 880px;
  margin: 0 auto;
  padding: 3rem 2rem 5rem;
}

/* ===== Header ===== */
.header {
  text-align: center;
  margin-bottom: 3rem;
  padding-bottom: 2rem;
  border-bottom: 1px solid var(--border-glass);
  position: relative;
}

.header h1 {
  font-size: 2.2rem;
  font-weight: 700;
  letter-spacing: -0.03em;
  background: linear-gradient(135deg, var(--h1-gradient-start) 0%, var(--h1-gradient-mid) 50%, var(--h1-gradient-end) 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  margin-bottom: 0.75rem;
  line-height: 1.3;
}

.header p {
  font-size: 0.95rem;
  color: var(--text-muted);
  max-width: 420px;
  margin: 0 auto;
  line-height: 1.7;
}

/* ===== Theme Toggle ===== */
.theme-toggle {
  position: absolute;
  top: 0;
  right: 0;
  width: 42px;
  height: 42px;
  border-radius: 50%;
  border: 1px solid var(--border-glass);
  background: var(--bg-glass);
  color: var(--text-secondary);
  font-size: 1.15rem;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: background var(--transition), border-color var(--transition), color var(--transition), transform var(--transition);
  backdrop-filter: blur(8px);
  line-height: 1;
}

.theme-toggle:hover {
  background: var(--bg-hover);
  border-color: var(--border-hover);
  color: var(--text-primary);
  transform: scale(1.08);
}

.theme-toggle:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
}

.theme-toggle .icon-sun,
.theme-toggle .icon-moon {
  position: absolute;
  transition: opacity var(--transition), transform var(--transition);
}

.theme-toggle .icon-moon {
  opacity: 1;
  transform: rotate(0deg);
}

.theme-toggle .icon-sun {
  opacity: 0;
  transform: rotate(-90deg);
}

[data-theme="dark"] .theme-toggle .icon-moon {
  opacity: 0;
  transform: rotate(90deg);
}

[data-theme="dark"] .theme-toggle .icon-sun {
  opacity: 1;
  transform: rotate(0deg);
}

/* ===== Drop Zone ===== */
.drop-zone {
  position: relative;
  border: 2px dashed var(--accent-glow);
  border-radius: var(--radius);
  padding: 3.5rem 2rem;
  text-align: center;
  cursor: pointer;
  transition: border-color var(--transition-slow), transform var(--transition-slow), box-shadow var(--transition-slow);
  background: linear-gradient(135deg, rgba(var(--accent-rgb), 0.03), rgba(var(--accent-rgb), 0.01));
}

.drop-zone::before {
  content: '';
  position: absolute;
  inset: -1px;
  border-radius: var(--radius);
  background: linear-gradient(135deg, rgba(var(--accent-rgb), 0.1), transparent, rgba(var(--accent-rgb), 0.08));
  opacity: 0;
  transition: opacity var(--transition-slow);
  z-index: -1;
}

.drop-zone:hover {
  border-color: rgba(var(--accent-rgb), 0.45);
  transform: translateY(-1px);
}

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

.drop-zone.dragover {
  border-color: var(--accent);
  box-shadow: 0 0 60px var(--accent-glow), inset 0 0 60px rgba(var(--accent-rgb), 0.05);
  transform: scale(1.005);
}

.drop-zone-icon {
  font-size: 3.5rem;
  margin-bottom: 1.25rem;
  display: block;
  opacity: 0.65;
  transition: opacity var(--transition), transform var(--transition);
}

.drop-zone:hover .drop-zone-icon,
.drop-zone.dragover .drop-zone-icon {
  opacity: 0.9;
  transform: scale(1.08);
}

.drop-zone-text {
  font-size: 1.05rem;
  font-weight: 500;
  color: var(--text-secondary);
  margin-bottom: 0.5rem;
}

.drop-zone-hint {
  font-size: 0.8rem;
  color: var(--text-muted);
  line-height: 1.6;
}

.drop-zone input[type="file"] {
  position: absolute;
  inset: 0;
  opacity: 0;
  cursor: pointer;
}

/* ===== Settings Panel ===== */
.settings-panel {
  display: flex;
  gap: 0.75rem 1.25rem;
  align-items: center;
  flex-wrap: wrap;
  margin-top: 1.25rem;
  padding: 1rem 1.5rem;
  background: var(--bg-glass);
  border: 1px solid var(--border-glass);
  border-radius: var(--radius-md);
  backdrop-filter: blur(16px);
}

.settings-panel label {
  font-size: 0.82rem;
  color: var(--text-muted);
  font-weight: 500;
  letter-spacing: 0.01em;
  white-space: nowrap;
}

.settings-panel select {
  appearance: none;
  -webkit-appearance: none;
  background-color: var(--bg-secondary);
  color: var(--text-primary);
  border: 1px solid var(--border-glass);
  border-radius: 8px;
  padding: 0.5rem 2rem 0.5rem 0.75rem;
  font-size: 0.82rem;
  font-family: inherit;
  outline: none;
  cursor: pointer;
  transition: border-color var(--transition), box-shadow var(--transition);
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='12' fill='var(--select-arrow)' viewBox='0 0 16 16'%3E%3Cpath d='M8 11L3 6h10z'/%3E%3C/svg%3E");
  background-repeat: no-repeat;
  background-position: right 0.6rem center;
}

.settings-panel select:hover {
  border-color: var(--border-hover);
}

.settings-panel select:focus {
  border-color: var(--accent);
  box-shadow: 0 0 0 3px var(--accent-soft);
}

.settings-divider {
  width: 1px;
  height: 24px;
  background: var(--border-glass);
  flex-shrink: 0;
}

.image-count {
  margin-left: auto;
  font-size: 0.82rem;
  color: var(--accent);
  font-weight: 600;
  font-variant-numeric: tabular-nums;
  background: var(--accent-soft);
  padding: 0.3rem 0.75rem;
  border-radius: var(--radius);
  letter-spacing: 0.02em;
}

/* ===== Preview Grid ===== */
.preview-section {
  margin-top: 2.5rem;
}

.preview-section h2 {
  font-size: 0.9rem;
  font-weight: 600;
  color: var(--text-muted);
  margin-bottom: 1.25rem;
  display: flex;
  align-items: center;
  gap: 0.5rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.preview-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(145px, 1fr));
  gap: 0.875rem;
  min-height: 60px;
}

/* ===== Preview Card ===== */
.preview-card {
  position: relative;
  border-radius: var(--radius-sm);
  overflow: hidden;
  background: var(--bg-secondary);
  border: 1px solid var(--border-glass);
  cursor: grab;
  transition: transform var(--transition), border-color var(--transition), box-shadow var(--transition);
  animation: cardIn 0.4s ease-out both;
}

@keyframes cardIn {
  from {
    opacity: 0;
    transform: scale(0.92) translateY(12px);
  }
  to {
    opacity: 1;
    transform: scale(1) translateY(0);
  }
}

.preview-card:hover {
  border-color: var(--border-hover);
  transform: translateY(-3px);
  box-shadow: var(--shadow);
}

.preview-card:active {
  cursor: grabbing;
}

.preview-card.sortable-ghost {
  opacity: 0.35;
  border-color: var(--accent);
  border-style: dashed;
}

.preview-card.sortable-chosen {
  box-shadow: 0 0 24px var(--accent-glow);
  border-color: var(--accent);
  z-index: 10;
}

.preview-card img {
  width: 100%;
  aspect-ratio: 1;
  object-fit: cover;
  display: block;
}

.preview-card-info {
  padding: 0.55rem 0.65rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
  background: var(--card-info-bg);
  border-top: 1px solid var(--card-info-border);
}

.preview-card-name {
  font-size: 0.68rem;
  color: var(--text-muted);
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
  max-width: 75px;
}

.preview-card-order {
  font-size: 0.62rem;
  font-weight: 700;
  color: var(--accent);
  background: var(--accent-soft);
  padding: 0.15rem 0.45rem;
  border-radius: 5px;
  font-variant-numeric: tabular-nums;
  letter-spacing: 0.03em;
}

.preview-card-remove {
  position: absolute;
  top: 6px;
  right: 6px;
  width: 26px;
  height: 26px;
  border-radius: 50%;
  border: none;
  background: var(--remove-btn-bg);
  color: #fff;
  font-size: 0.75rem;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  opacity: 0;
  transition: opacity var(--transition), transform var(--transition), background var(--transition);
}

.preview-card:hover .preview-card-remove {
  opacity: 1;
}

.preview-card-remove:hover {
  background: var(--danger);
  color: #fff;
  transform: scale(1.15);
  box-shadow: 0 2px 12px rgba(var(--danger-rgb), 0.3);
}

/* ===== Actions ===== */
.actions {
  margin-top: 2.5rem;
  display: flex;
  gap: 0.875rem;
  justify-content: center;
  flex-wrap: wrap;
}

.btn {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.9rem 2.25rem;
  border: none;
  border-radius: 12px;
  font-size: 0.9rem;
  font-weight: 600;
  font-family: inherit;
  cursor: pointer;
  transition: transform var(--transition), box-shadow var(--transition), filter var(--transition), background var(--transition), color var(--transition), border-color var(--transition);
  position: relative;
  overflow: hidden;
  letter-spacing: 0.01em;
}

.btn::after {
  content: '';
  position: absolute;
  inset: 0;
  background: radial-gradient(circle at 50% 50%, rgba(255, 255, 255, 0.2) 0%, transparent 60%);
  opacity: 0;
  transition: opacity 0.5s;
}

.btn:active::after {
  opacity: 1;
  transition: opacity 0s;
}

.btn-primary {
  background: linear-gradient(135deg, var(--accent), var(--accent-light));
  color: #fff;
  box-shadow: 0 4px 20px var(--accent-glow);
}

.btn-primary:hover:not(:disabled) {
  transform: translateY(-2px);
  box-shadow: 0 8px 32px rgba(var(--accent-rgb), 0.4);
  filter: brightness(1.05);
}

.btn-primary:active:not(:disabled) {
  transform: translateY(0);
  box-shadow: 0 2px 12px var(--accent-glow);
}

.btn-primary:disabled {
  opacity: 0.35;
  cursor: not-allowed;
  filter: saturate(0.5);
}

.btn-secondary {
  background: var(--bg-glass);
  border: 1px solid var(--border-glass);
  color: var(--text-secondary);
  backdrop-filter: blur(8px);
}

.btn-secondary:hover {
  background: var(--bg-hover);
  color: var(--text-primary);
  border-color: var(--border-hover);
  transform: translateY(-1px);
}

/* Focus styles for accessibility */
.btn:focus-visible,
.settings-panel select:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
}

/* ===== Progress ===== */
.progress-overlay {
  position: fixed;
  inset: 0;
  background: var(--overlay-bg);
  backdrop-filter: blur(12px);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 1000;
  opacity: 0;
  pointer-events: none;
  transition: opacity var(--transition-slow);
}

.progress-overlay.active {
  opacity: 1;
  pointer-events: all;
}

.progress-box {
  background: var(--bg-secondary);
  border: 1px solid var(--border-glass);
  border-radius: var(--radius);
  padding: 2.5rem 3rem;
  text-align: center;
  box-shadow: var(--shadow-lg);
  min-width: 340px;
  max-width: 90vw;
  animation: progressBoxIn 0.4s ease-out;
}

@keyframes progressBoxIn {
  from {
    opacity: 0;
    transform: scale(0.95) translateY(10px);
  }
  to {
    opacity: 1;
    transform: scale(1) translateY(0);
  }
}

.progress-box h3 {
  font-size: 1.05rem;
  font-weight: 600;
  margin-bottom: 1.5rem;
  color: var(--text-primary);
}

.progress-bar-track {
  width: 100%;
  height: 5px;
  background: var(--progress-track);
  border-radius: 3px;
  overflow: hidden;
  margin-bottom: 1rem;
}

.progress-bar-fill {
  height: 100%;
  width: 0%;
  background: linear-gradient(90deg, var(--accent), var(--accent-light));
  border-radius: 3px;
  transition: width 0.35s ease;
  box-shadow: 0 0 12px var(--accent-glow);
}

.progress-text {
  font-size: 0.82rem;
  color: var(--text-muted);
  font-variant-numeric: tabular-nums;
}

/* ===== Toast ===== */
.toast {
  position: fixed;
  bottom: 2rem;
  left: 50%;
  transform: translateX(-50%) translateY(20px);
  background: var(--bg-secondary);
  border: 1px solid var(--border-glass);
  color: var(--text-primary);
  padding: 0.85rem 1.75rem;
  border-radius: var(--radius-md);
  font-size: 0.85rem;
  font-weight: 500;
  box-shadow: var(--shadow);
  opacity: 0;
  pointer-events: none;
  transition: opacity var(--transition-slow), transform var(--transition-slow);
  z-index: 2000;
  backdrop-filter: blur(16px);
  max-width: 90vw;
}

.toast.show {
  opacity: 1;
  transform: translateX(-50%) translateY(0);
  pointer-events: all;
}

.toast.success {
  border-color: rgba(var(--success-rgb), 0.25);
  background: linear-gradient(135deg, var(--bg-secondary), rgba(var(--success-rgb), 0.05));
}

.toast.error {
  border-color: rgba(var(--danger-rgb), 0.25);
  background: linear-gradient(135deg, var(--bg-secondary), rgba(var(--danger-rgb), 0.05));
}

/* ===== Empty State ===== */
.empty-state {
  text-align: center;
  padding: 2rem;
  color: var(--text-muted);
  font-size: 0.85rem;
  grid-column: 1 / -1;
}

/* ===== Footer ===== */
.footer {
  margin-top: 4rem;
  text-align: center;
  font-size: 0.72rem;
  color: var(--text-muted);
  border-top: 1px solid var(--border-glass);
  padding-top: 1.5rem;
  letter-spacing: 0.02em;
}

/* ===== Scrollbar ===== */
::-webkit-scrollbar {
  width: 6px;
}

::-webkit-scrollbar-track {
  background: transparent;
}

::-webkit-scrollbar-thumb {
  background: var(--scrollbar-thumb);
  border-radius: 3px;
}

::-webkit-scrollbar-thumb:hover {
  background: var(--scrollbar-thumb-hover);
}

/* ===== Selection ===== */
::selection {
  background: rgba(var(--accent-rgb), 0.25);
  color: var(--text-primary);
}

/* ===== Responsive ===== */
@media (max-width: 600px) {
  .container {
    padding: 2rem 1.25rem 3rem;
  }

  .header {
    margin-bottom: 2rem;
    padding-bottom: 1.5rem;
  }

  .header h1 {
    font-size: 1.6rem;
  }

  .header p {
    font-size: 0.85rem;
  }

  .drop-zone {
    padding: 2.5rem 1.5rem;
  }

  .drop-zone-icon {
    font-size: 2.5rem;
  }

  .preview-grid {
    grid-template-columns: repeat(auto-fill, minmax(110px, 1fr));
    gap: 0.65rem;
  }

  .settings-panel {
    flex-direction: column;
    align-items: stretch;
    gap: 0.75rem;
    padding: 1rem 1.25rem;
  }

  .settings-panel label {
    margin-bottom: -0.25rem;
  }

  .settings-divider {
    display: none;
  }

  .image-count {
    margin-left: 0;
    text-align: center;
  }

  .btn {
    width: 100%;
    justify-content: center;
    padding: 1rem 2rem;
  }

  .actions {
    flex-direction: column;
  }

  .preview-card-remove {
    opacity: 0.8;
  }

  .theme-toggle {
    width: 36px;
    height: 36px;
    font-size: 1rem;
  }
}

/* ===== Reduced motion ===== */
@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }
}