:root {
  --color-bg: #f7f7f9;
  --color-text: #1f1f1f;
  --color-muted: #6b6b6b;
  --color-accent: #3b5bfd;
  --color-card-bg: #ffffff;
  --color-border: #e3e3e8;
  --color-danger: #c0392b;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;
  font-family: "Hiragino Kaku Gothic ProN", "Yu Gothic", -apple-system, BlinkMacSystemFont, sans-serif;
  background: var(--color-bg);
  color: var(--color-text);
}

.app {
  max-width: 900px;
  margin: 1rem auto 4rem;
  padding: 0 1.5rem;
}

.app h1 {
  margin: 0 0 0.5rem;
  font-size: 1.5rem;
  text-align: center;
}

.description {
  margin: 0 0 2rem;
  color: var(--color-muted);
  font-size: 0.9rem;
  text-align: center;
}

.url-form {
  display: flex;
  gap: 0.5rem;
  max-width: 640px;
  margin: 0 auto 1rem;
}

.url-form input[type="text"] {
  flex: 1;
  padding: 0.75rem 1rem;
  border-radius: 8px;
  border: 1px solid var(--color-border);
  font-size: 1rem;
}

.url-form input[type="text"]:focus {
  outline: 2px solid var(--color-accent);
  outline-offset: 1px;
}

.btn {
  padding: 0.75rem 1.5rem;
  border-radius: 8px;
  border: 1px solid var(--color-border);
  background: #fff;
  color: var(--color-text);
  font-size: 1rem;
  cursor: pointer;
  white-space: nowrap;
}

.btn:hover {
  background: #f0f0f4;
}

.btn-primary {
  background: var(--color-accent);
  border-color: var(--color-accent);
  color: #fff;
}

.btn-primary:hover {
  background: #2f4bd9;
}

.error-message {
  max-width: 640px;
  margin: 0 auto 1.5rem;
  padding: 0.75rem 1rem;
  border-radius: 8px;
  background: #fdecea;
  color: var(--color-danger);
  font-size: 0.9rem;
  text-align: center;
}

.video-id {
  text-align: center;
  color: var(--color-muted);
  font-size: 0.9rem;
  margin-bottom: 1.5rem;
}

.video-id code {
  background: #eee;
  padding: 0.1rem 0.4rem;
  border-radius: 4px;
}

.thumbnail-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
  gap: 1.25rem;
}

.thumbnail-card {
  background: var(--color-card-bg);
  border: 1px solid var(--color-border);
  border-radius: 12px;
  padding: 1rem;
  display: flex;
  flex-direction: column;
  gap: 0.6rem;
}

.thumbnail-card .thumb-frame {
  aspect-ratio: 16 / 9;
  background: #eee;
  border-radius: 8px;
  overflow: hidden;
  display: flex;
  align-items: center;
  justify-content: center;
}

.thumbnail-card img {
  width: 100%;
  height: 100%;
  object-fit: contain;
  display: block;
}

.thumbnail-card.unavailable .thumb-frame {
  color: var(--color-muted);
  font-size: 0.85rem;
}

.thumbnail-card.unavailable img {
  display: none;
}

.thumb-label {
  display: flex;
  justify-content: space-between;
  align-items: baseline;
  font-size: 0.9rem;
}

.thumb-label .name {
  font-weight: 600;
}

.thumb-label .size {
  color: var(--color-muted);
  font-variant-numeric: tabular-nums;
  font-size: 0.8rem;
}

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

.thumb-actions .btn {
  flex: 1;
  padding: 0.5rem;
  font-size: 0.85rem;
  text-align: center;
  text-decoration: none;
}

.thumbnail-card.unavailable .thumb-actions {
  display: none;
}