/* ─── Design tokens ─────────────────────────────── */
:root {
  --bg:              #030712;
  --bg-card:         #111827;
  --bg-card-border:  #1f2937;
  --bg-hover:        rgba(17, 24, 39, 0.4);
  --bg-drag:         rgba(30, 27, 75, 0.3);
  --bg-danger-hover: rgba(69, 10, 10, 0.4);
  --bg-error:        rgba(69, 10, 10, 0.3);
  --text:            #e5e7eb;
  --text-strong:     #ffffff;
  --text-body:       #d1d5db;
  --text-muted:      #6b7280;
  --text-faint:      #4b5563;
  --border:          #374151;
  --accent:          #6366f1;
  --accent-soft:     #818cf8;
  --error:           #f87171;
  --error-border:    rgba(127, 29, 29, 0.4);
}

@media (prefers-color-scheme: light) {
  :root:not([data-theme="dark"]) {
    --bg:              #f9fafb;
    --bg-card:         #ffffff;
    --bg-card-border:  #e5e7eb;
    --bg-hover:        rgba(238, 242, 255, 0.6);
    --bg-drag:         rgba(199, 210, 254, 0.3);
    --bg-danger-hover: rgba(254, 226, 226, 0.6);
    --bg-error:        rgba(254, 226, 226, 0.5);
    --text:            #111827;
    --text-strong:     #030712;
    --text-body:       #374151;
    --text-muted:      #6b7280;
    --text-faint:      #9ca3af;
    --border:          #d1d5db;
    --accent:          #6366f1;
    --accent-soft:     #4f46e5;
    --error:           #dc2626;
    --error-border:    rgba(252, 165, 165, 0.5);
  }
}

:root[data-theme="light"] {
  --bg:              #f9fafb;
  --bg-card:         #ffffff;
  --bg-card-border:  #e5e7eb;
  --bg-hover:        rgba(238, 242, 255, 0.6);
  --bg-drag:         rgba(199, 210, 254, 0.3);
  --bg-danger-hover: rgba(254, 226, 226, 0.6);
  --bg-error:        rgba(254, 226, 226, 0.5);
  --text:            #111827;
  --text-strong:     #030712;
  --text-body:       #374151;
  --text-muted:      #6b7280;
  --text-faint:      #9ca3af;
  --border:          #d1d5db;
  --accent:          #6366f1;
  --accent-soft:     #4f46e5;
  --error:           #dc2626;
  --error-border:    rgba(252, 165, 165, 0.5);
}

/* ─── Base ───────────────────────────────────────── */
*, *::before, *::after {
  box-sizing: border-box;
}

body {
  margin: 0;
  background-color: var(--bg);
  font-family: -apple-system, "San Francisco", "Helvetica Neue", "Segoe UI", "DejaVu Sans", "Noto Sans", system-ui, sans-serif;
}

/* ─── Layout ─────────────────────────────────────── */
.page {
  min-height: 100vh;
  background-color: var(--bg);
  color: var(--text);
  display: flex;
  justify-content: center;
  padding: 3.5rem 1.5rem;
  transition: background-color 200ms, color 200ms;
}

.content {
  width: 100%;
  max-width: 32rem;
  display: flex;
  flex-direction: column;
  gap: 1.25rem;
}

/* ─── Header ─────────────────────────────────────── */
.header h1 {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--text-strong);
  letter-spacing: -0.025em;
}

.header p {
  font-size: 0.875rem;
  color: var(--text-muted);
  margin-top: 0.25rem;
}

/* ─── Theme switcher ─────────────────────────────── */
.theme-btn {
  position: fixed;
  top: 1rem;
  right: 1rem;
  background-color: var(--bg-card);
  border: 1px solid var(--border);
  color: var(--text-muted);
  cursor: pointer;
  font-size: 1rem;
  line-height: 1;
  padding: 0.5rem 0.625rem;
  border-radius: 0.5rem;
  transition: background-color 150ms, border-color 150ms, color 150ms;
}

.theme-btn:hover {
  background-color: var(--bg-card-border);
  color: var(--text-body);
}

/* ─── Drop zone ──────────────────────────────────── */
.drop-zone {
  border: 2px dashed var(--border);
  border-radius: 1rem;
  padding: 4rem;
  text-align: center;
  cursor: pointer;
  user-select: none;
  transition: border-color 150ms, background-color 150ms;
}

.drop-zone:hover {
  border-color: var(--accent);
  background-color: var(--bg-hover);
}

.drop-zone.dragging {
  border-color: var(--accent);
  background-color: var(--bg-drag);
}

.drop-zone .icon {
  display: block;
  font-size: 2.25rem;
  margin-bottom: 0.75rem;
  color: var(--accent-soft);
}

.drop-zone .title {
  color: var(--text-body);
  font-weight: 500;
}

.drop-zone .hint {
  font-size: 0.875rem;
  color: var(--text-faint);
  margin-top: 0.25rem;
}

/* ─── File list ──────────────────────────────────── */
.file-list {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
  list-style: none;
  padding: 0;
  margin: 0;
}

.file-item {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  background-color: var(--bg-card);
  border: 1px solid var(--bg-card-border);
  border-radius: 0.75rem;
  padding: 0.75rem 1rem;
  transition: background-color 200ms;
}

.file-item .file-icon {
  color: var(--accent-soft);
  font-size: 1.125rem;
  flex-shrink: 0;
}

.file-item .file-name {
  flex: 1;
  font-size: 0.875rem;
  color: var(--text-body);
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.file-item .remove-btn {
  color: var(--text-faint);
  border-radius: 0.375rem;
  padding: 0.25rem 0.5rem;
  font-size: 0.875rem;
  transition: color 150ms, background-color 150ms;
  flex-shrink: 0;
  cursor: pointer;
  background: none;
  border: none;
}

.file-item .remove-btn:hover {
  color: var(--error);
  background-color: var(--bg-danger-hover);
}

/* ─── Error message ──────────────────────────────── */
.error-msg {
  font-size: 0.875rem;
  color: var(--error);
  background-color: var(--bg-error);
  border: 1px solid var(--error-border);
  border-radius: 0.75rem;
  padding: 0.75rem 1rem;
}

/* ─── Merge button ───────────────────────────────── */
.merge-btn {
  width: 100%;
  padding: 0.75rem 0;
  background-color: var(--accent);
  color: #ffffff;
  font-weight: 600;
  border-radius: 0.75rem;
  transition: background-color 150ms;
  cursor: pointer;
  border: none;
  font-size: 1rem;
}

.merge-btn:hover:not(:disabled) {
  background-color: var(--accent-soft);
}

.merge-btn:disabled {
  background-color: var(--bg-card-border);
  color: var(--text-faint);
  cursor: not-allowed;
}

/* ─── Feature list ───────────────────────────────── */
.features {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 0.625rem 1rem;
  list-style: none;
  padding: 0;
  margin: 0;
}

.features li {
  font-size: 0.8125rem;
  color: var(--text-muted);
}