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

:root {
  --bg:           #f4f6fb;
  --surface:      #ffffff;
  --card:         #ffffff;
  --card-hover:   #f0f2ff;
  --border:       rgba(0,0,0,0.08);
  --border-hover: rgba(0,0,0,0.15);
  --accent:       #6366f1;
  --accent-dim:   rgba(99,102,241,0.18);
  --accent-light: #818cf8;
  --text:         #1e1e2e;
  --text-muted:   #6b7280;
  --text-dim:     #9ca3af;
  --success:      #059669;
  --warn:         #d97706;
  --error:        #dc2626;
  --r:            12px;
  --r-sm:         8px;
  --r-lg:         18px;
}

html { scroll-behavior: smooth; }

body {
  background: var(--bg);
  color: var(--text);
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', system-ui, sans-serif;
  font-size: 15px;
  line-height: 1.6;
  min-height: 100vh;
  -webkit-font-smoothing: antialiased;
}

/* ===== App ===== */
.app {
  max-width: 860px;
  margin: 0 auto;
  padding: 2.5rem 1.5rem 5rem;
}

/* ===== Header ===== */
.header {
  text-align: center;
  margin-bottom: 2.5rem;
}

.logo {
  display: inline-flex;
  align-items: center;
  gap: 0.6rem;
  margin-bottom: 0.5rem;
}

.logo-mark {
  width: 36px;
  height: 36px;
  flex-shrink: 0;
}

.logo h1 {
  font-size: 2rem;
  font-weight: 800;
  letter-spacing: -0.5px;
  background: linear-gradient(135deg, var(--accent), #4f46e5);
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
}

.tagline {
  color: var(--text-muted);
  font-size: 0.9rem;
}

/* ===== Browser Warning ===== */
.browser-warning {
  display: flex;
  align-items: flex-start;
  gap: 0.625rem;
  background: rgba(245,158,11,0.08);
  border: 1px solid rgba(245,158,11,0.25);
  border-radius: var(--r);
  padding: 0.875rem 1.125rem;
  margin-bottom: 1.5rem;
  color: var(--warn);
  font-size: 0.875rem;
  line-height: 1.5;
}

.browser-warning svg { flex-shrink: 0; margin-top: 1px; }

/* ===== Settings Panel ===== */
.settings-panel {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--r);
  padding: 1.25rem 1.5rem;
  margin-bottom: 1.25rem;
  display: flex;
  gap: 2.5rem;
  align-items: flex-start;
  flex-wrap: wrap;
}

.setting-group { flex: 1; min-width: 200px; }

.setting-group--side {
  flex: none;
  display: flex;
  flex-direction: column;
  justify-content: center;
  padding-top: 0.25rem;
}

.setting-label {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 0.625rem;
  font-size: 0.8rem;
  font-weight: 600;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.quality-badge {
  background: var(--accent);
  color: #fff;
  font-size: 0.75rem;
  font-weight: 700;
  min-width: 2.25rem;
  text-align: center;
  padding: 0.1rem 0.45rem;
  border-radius: 999px;
}

/* Slider */
.quality-slider {
  -webkit-appearance: none;
  appearance: none;
  width: 100%;
  height: 5px;
  border-radius: 3px;
  outline: none;
  cursor: pointer;
  transition: opacity 0.2s;
}

.quality-slider:disabled { opacity: 0.35; cursor: not-allowed; }

.quality-slider::-webkit-slider-thumb {
  -webkit-appearance: none;
  width: 18px;
  height: 18px;
  border-radius: 50%;
  background: var(--accent);
  cursor: pointer;
  box-shadow: 0 0 0 3px var(--accent-dim), 0 1px 4px rgba(0,0,0,0.2);
  transition: box-shadow 0.15s, transform 0.15s;
}

.quality-slider:not(:disabled)::-webkit-slider-thumb:hover {
  box-shadow: 0 0 0 6px var(--accent-dim), 0 1px 4px rgba(0,0,0,0.2);
  transform: scale(1.1);
}

.quality-slider::-moz-range-thumb {
  width: 18px;
  height: 18px;
  border: none;
  border-radius: 50%;
  background: var(--accent);
  cursor: pointer;
  box-shadow: 0 0 0 3px var(--accent-dim);
}

.slider-labels {
  display: flex;
  justify-content: space-between;
  margin-top: 0.5rem;
  font-size: 0.72rem;
  color: var(--text-dim);
}

/* Toggle Switch */
.toggle-label {
  display: flex;
  align-items: center;
  gap: 0.625rem;
  cursor: pointer;
  user-select: none;
  font-size: 0.9rem;
  color: var(--text);
}

.toggle-input { display: none; }

.toggle-track {
  position: relative;
  width: 40px;
  height: 22px;
  background: #d1d5db;
  border-radius: 999px;
  transition: background 0.2s;
  flex-shrink: 0;
}

.toggle-input:checked ~ .toggle-track { background: var(--accent); }

.toggle-thumb {
  position: absolute;
  top: 3px;
  left: 3px;
  width: 16px;
  height: 16px;
  border-radius: 50%;
  background: #fff;
  transition: transform 0.2s;
  box-shadow: 0 1px 3px rgba(0,0,0,0.25);
}

.toggle-input:checked ~ .toggle-track .toggle-thumb { transform: translateX(18px); }

.setting-note {
  margin-top: 0.5rem;
  font-size: 0.75rem;
  color: var(--text-dim);
  line-height: 1.4;
}

/* ===== Drop Zone ===== */
.drop-zone {
  border: 2px dashed #c7d2fe;
  border-radius: var(--r-lg);
  padding: 3.5rem 2rem;
  text-align: center;
  cursor: pointer;
  transition: border-color 0.2s, background 0.2s, transform 0.2s, box-shadow 0.2s;
  background: var(--surface);
  margin-bottom: 2rem;
  position: relative;
  outline: none;
}

.drop-zone:hover,
.drop-zone:focus-visible {
  border-color: var(--accent);
  background: rgba(99,102,241,0.04);
}

.drop-zone.dragover {
  border-color: var(--accent);
  background: rgba(99,102,241,0.05);
  transform: scale(1.008);
  box-shadow: 0 0 0 5px var(--accent-dim), 0 12px 40px rgba(99,102,241,0.15);
}

.drop-zone-content { pointer-events: none; }

.drop-icon {
  color: var(--accent);
  opacity: 0.75;
  margin-bottom: 1rem;
  transition: transform 0.2s, opacity 0.2s;
}

.drop-zone.dragover .drop-icon { transform: translateY(-4px); opacity: 1; }

.drop-title {
  font-size: 1.15rem;
  font-weight: 600;
  margin-bottom: 0.3rem;
}

.drop-or {
  font-size: 0.85rem;
  color: var(--text-dim);
  margin-bottom: 0.875rem;
}

.drop-formats {
  margin-top: 0.875rem;
  font-size: 0.78rem;
  color: var(--text-dim);
}

/* ===== Buttons ===== */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  padding: 0.55rem 1.1rem;
  border-radius: var(--r-sm);
  font-size: 0.875rem;
  font-weight: 600;
  cursor: pointer;
  border: none;
  transition: background 0.15s, transform 0.15s, box-shadow 0.15s, opacity 0.15s;
  white-space: nowrap;
}

.btn:disabled { opacity: 0.5; cursor: not-allowed; }
.btn:not(:disabled):active { transform: scale(0.97); }

.btn--primary {
  background: var(--accent);
  color: #fff;
  pointer-events: all;
}
.btn--primary:not(:disabled):hover {
  background: var(--accent-light);
  box-shadow: 0 4px 16px var(--accent-dim);
}

.btn--secondary {
  background: var(--card);
  color: var(--text);
  border: 1px solid var(--border-hover);
}
.btn--secondary:not(:disabled):hover { background: var(--card-hover); }

.btn--ghost {
  background: transparent;
  color: var(--text-muted);
  border: 1px solid transparent;
}
.btn--ghost:not(:disabled):hover { background: var(--card); color: var(--text); }

/* ===== Results ===== */
.results-section { animation: fadeUp 0.3s ease; }

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

.results-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 1rem;
  flex-wrap: wrap;
  gap: 0.75rem;
}

.results-meta { display: flex; align-items: center; gap: 0.75rem; flex-wrap: wrap; }

.results-title {
  font-size: 1rem;
  font-weight: 700;
}

.summary {
  font-size: 0.8rem;
  color: var(--text-muted);
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 999px;
  padding: 0.2rem 0.75rem;
}

.results-actions { display: flex; gap: 0.5rem; }

/* ===== File Grid ===== */
.file-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(230px, 1fr));
  gap: 0.875rem;
}

/* ===== File Card ===== */
.file-card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--r);
  overflow: hidden;
  transition: border-color 0.2s, transform 0.2s, box-shadow 0.2s;
  animation: fadeUp 0.25s ease;
}

.file-card:not(.loading):hover {
  border-color: var(--accent);
  transform: translateY(-2px);
  box-shadow: 0 8px 28px rgba(99,102,241,0.12);
}

.file-card.error { border-color: rgba(239,68,68,0.25); }

/* Card Preview */
.card-preview {
  position: relative;
  aspect-ratio: 16 / 9;
  background: #f1f3f9;
  overflow: hidden;
}

.preview-img {
  width: 100%;
  height: 100%;
  object-fit: contain;
  padding: 6px;
}

.loading-overlay {
  position: absolute;
  inset: 0;
  background: rgba(241,243,249,0.75);
  display: flex;
  align-items: center;
  justify-content: center;
  backdrop-filter: blur(3px);
}

.spinner {
  width: 30px;
  height: 30px;
  border: 3px solid rgba(99,102,241,0.2);
  border-top-color: var(--accent);
  border-radius: 50%;
  animation: spin 0.75s linear infinite;
}

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

/* Card Info */
.card-info {
  padding: 0.75rem 0.875rem 0.625rem;
  border-top: 1px solid var(--border);
}

.card-filename {
  font-size: 0.8rem;
  font-weight: 500;
  color: var(--text);
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
  margin-bottom: 0.4rem;
}

.card-sizes {
  display: flex;
  align-items: center;
  gap: 0.3rem;
  font-size: 0.78rem;
  color: var(--text-muted);
  flex-wrap: wrap;
}

.size-original { color: var(--text-dim); }
.size-arrow { color: var(--text-dim); font-size: 0.7rem; }
.size-converted { font-weight: 700; color: var(--text); }

.card-savings {
  margin-top: 0.3rem;
  font-size: 0.75rem;
  font-weight: 700;
}

.savings-good { color: var(--success); }
.savings-warn { color: var(--warn); }

.card-error-msg {
  margin-top: 0.4rem;
  font-size: 0.775rem;
  color: var(--error);
}

/* Card Actions */
.card-actions {
  padding: 0.625rem 0.875rem 0.75rem;
  border-top: 1px solid var(--border);
}

.card-dl-btn {
  width: 100%;
  padding: 0.45rem;
  background: var(--accent);
  color: #fff;
  border: none;
  border-radius: var(--r-sm);
  font-size: 0.825rem;
  font-weight: 600;
  cursor: pointer;
  transition: background 0.15s, box-shadow 0.15s, transform 0.1s;
}

.card-dl-btn:not(:disabled):hover {
  background: var(--accent-light);
  box-shadow: 0 4px 14px var(--accent-dim);
}

.card-dl-btn:not(:disabled):active { transform: scale(0.97); }

.card-dl-btn:disabled { opacity: 0.35; cursor: not-allowed; }

/* ===== Footer ===== */
.footer {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 0.4rem;
  margin-top: 3rem;
  font-size: 0.78rem;
  color: var(--text-dim);
}

/* ===== Utility ===== */
.hidden { display: none !important; }

/* ===== Responsive ===== */
@media (max-width: 600px) {
  .app { padding: 1.75rem 1rem 4rem; }
  .logo h1 { font-size: 1.6rem; }
  .settings-panel { flex-direction: column; gap: 1.25rem; }
  .setting-group--side { padding-top: 0; }
  .drop-zone { padding: 2.5rem 1rem; }
  .results-header { flex-direction: column; align-items: flex-start; }
  .file-grid { grid-template-columns: 1fr 1fr; }
}

@media (max-width: 400px) {
  .file-grid { grid-template-columns: 1fr; }
}