:root {
  --bg-color: #0d1117;
  --card-bg: #161b22;
  --card-border: #30363d;
  --input-bg: #0d1117;
  --text-primary: #f0f6fc;
  --text-secondary: #8b949e;
  --yt-red: #ff0033;
  --yt-red-hover: #cc0029;
  --accent-blue: #58a6ff;
  --accent-green: #238636;
  --accent-green-hover: #2ea043;
  --badge-hd: #ff7b72;
  --radius: 12px;
  --transition: all 0.2s ease-in-out;
}

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body {
  font-family: 'Pretendard', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  background-color: var(--bg-color);
  color: var(--text-primary);
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  align-items: center;
  padding: 40px 20px;
}

.container {
  width: 100%;
  max-width: 960px;
}

/* Header */
.header {
  text-align: center;
  margin-bottom: 32px;
}

.logo {
  display: inline-flex;
  align-items: center;
  gap: 12px;
  margin-bottom: 8px;
}

.yt-icon {
  width: 42px;
  height: 42px;
  color: var(--yt-red);
}

.logo h1 {
  font-size: 1.85rem;
  font-weight: 800;
  letter-spacing: -0.5px;
}

.subtitle {
  color: var(--text-secondary);
  font-size: 0.95rem;
}

/* Search Card */
.search-card {
  background: var(--card-bg);
  border: 1px solid var(--card-border);
  border-radius: var(--radius);
  padding: 24px;
  box-shadow: 0 8px 24px rgba(0, 0, 0, 0.4);
  margin-bottom: 32px;
}

.search-form {
  display: flex;
  gap: 12px;
  margin-bottom: 16px;
}

@media (max-width: 680px) {
  .search-form {
    flex-direction: column;
  }
}

.input-wrapper {
  position: relative;
  flex: 1;
  display: flex;
  align-items: center;
}

.search-icon {
  position: absolute;
  left: 14px;
  width: 20px;
  height: 20px;
  color: var(--text-secondary);
  pointer-events: none;
}

.input-wrapper input {
  width: 100%;
  background: var(--input-bg);
  border: 1px solid var(--card-border);
  border-radius: 8px;
  padding: 14px 80px 14px 44px;
  color: var(--text-primary);
  font-size: 1rem;
  outline: none;
  transition: var(--transition);
}

.input-wrapper input:focus {
  border-color: var(--accent-blue);
  box-shadow: 0 0 0 3px rgba(88, 166, 255, 0.2);
}

.paste-btn {
  position: absolute;
  right: 10px;
  background: #21262d;
  border: 1px solid var(--card-border);
  border-radius: 6px;
  color: var(--text-secondary);
  font-size: 0.8rem;
  padding: 6px 10px;
  cursor: pointer;
  transition: var(--transition);
}

.paste-btn:hover {
  background: #30363d;
  color: var(--text-primary);
}

.submit-btn {
  background: var(--yt-red);
  color: white;
  border: none;
  border-radius: 8px;
  padding: 14px 28px;
  font-size: 1rem;
  font-weight: 700;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  transition: var(--transition);
  min-width: 130px;
}

.submit-btn:hover {
  background: var(--yt-red-hover);
  transform: translateY(-1px);
}

.submit-btn:disabled {
  opacity: 0.6;
  cursor: not-allowed;
  transform: none;
}

/* Spinner */
.spinner {
  display: none;
  width: 18px;
  height: 18px;
  border: 2px solid rgba(255, 255, 255, 0.3);
  border-top-color: white;
  border-radius: 50%;
  animation: spin 0.8s linear infinite;
}

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

/* Error Box */
.error-box {
  background: rgba(248, 81, 73, 0.15);
  border: 1px solid rgba(248, 81, 73, 0.4);
  color: #ff7b72;
  border-radius: 8px;
  padding: 12px 16px;
  font-size: 0.9rem;
  margin-bottom: 16px;
}

/* Examples */
.examples {
  display: flex;
  align-items: center;
  flex-wrap: wrap;
  gap: 8px;
  font-size: 0.82rem;
  color: var(--text-secondary);
}

.examples code {
  background: #21262d;
  padding: 3px 8px;
  border-radius: 4px;
  color: #c9d1d9;
}

/* Video Info Card */
.video-info-card {
  background: var(--card-bg);
  border: 1px solid var(--card-border);
  border-radius: var(--radius);
  padding: 20px 24px;
  margin-bottom: 28px;
}

.video-channel {
  display: inline-block;
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--accent-blue);
  margin-bottom: 6px;
}

.video-title {
  font-size: 1.25rem;
  font-weight: 700;
  margin-bottom: 10px;
  line-height: 1.4;
}

.video-link {
  color: var(--text-secondary);
  font-size: 0.85rem;
  text-decoration: none;
  display: inline-flex;
  align-items: center;
  gap: 4px;
  transition: var(--transition);
}

.video-link:hover {
  color: var(--accent-blue);
  text-decoration: underline;
}

/* Section Title */
.section-title-wrapper {
  margin-bottom: 20px;
}

.section-title {
  font-size: 1.2rem;
  font-weight: 700;
  margin-bottom: 4px;
}

.section-desc {
  font-size: 0.85rem;
  color: var(--text-secondary);
}

/* Thumbnails Grid */
.thumbnails-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 20px;
  margin-bottom: 40px;
}

.thumb-card {
  background: var(--card-bg);
  border: 1px solid var(--card-border);
  border-radius: var(--radius);
  overflow: hidden;
  display: flex;
  flex-direction: column;
  transition: var(--transition);
}

.thumb-card:hover {
  border-color: #58a6ff;
  transform: translateY(-3px);
  box-shadow: 0 10px 20px rgba(0, 0, 0, 0.4);
}

.thumb-img-wrapper {
  position: relative;
  width: 100%;
  padding-top: 56.25%; /* 16:9 Aspect Ratio */
  background: #000;
  overflow: hidden;
}

.thumb-img {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  object-fit: cover;
  transition: var(--transition);
}

.badge {
  position: absolute;
  top: 10px;
  left: 10px;
  background: rgba(0, 0, 0, 0.75);
  backdrop-filter: blur(4px);
  color: #fff;
  font-size: 0.75rem;
  font-weight: 700;
  padding: 4px 8px;
  border-radius: 4px;
}

.badge.recommended {
  background: var(--yt-red);
  box-shadow: 0 2px 8px rgba(255, 0, 51, 0.4);
}

.thumb-body {
  padding: 16px;
  display: flex;
  flex-direction: column;
  flex: 1;
  gap: 12px;
}

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

.thumb-name {
  font-size: 0.95rem;
  font-weight: 600;
}

.thumb-res {
  font-size: 0.8rem;
  color: var(--text-secondary);
  background: #21262d;
  padding: 2px 6px;
  border-radius: 4px;
}

.thumb-actions {
  display: flex;
  gap: 8px;
  margin-top: auto;
}

.download-btn {
  flex: 1;
  background: var(--accent-green);
  color: white;
  border: none;
  border-radius: 6px;
  padding: 10px 14px;
  font-size: 0.9rem;
  font-weight: 600;
  cursor: pointer;
  text-decoration: none;
  text-align: center;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 6px;
  transition: var(--transition);
}

.download-btn:hover {
  background: var(--accent-green-hover);
}

.view-btn {
  background: #21262d;
  color: var(--text-primary);
  border: 1px solid var(--card-border);
  border-radius: 6px;
  padding: 10px 12px;
  font-size: 0.85rem;
  cursor: pointer;
  text-decoration: none;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  transition: var(--transition);
}

.view-btn:hover {
  background: #30363d;
}

/* SEO Info Section */
.seo-info-section {
  margin-top: 40px;
  margin-bottom: 40px;
  border-top: 1px solid var(--card-border);
  padding-top: 32px;
}

.seo-heading {
  font-size: 1.15rem;
  font-weight: 700;
  margin-bottom: 20px;
  color: var(--text-primary);
}

.seo-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: 16px;
}

.seo-card {
  background: var(--card-bg);
  border: 1px solid var(--card-border);
  border-radius: var(--radius);
  padding: 18px 20px;
}

.seo-card h3 {
  font-size: 0.95rem;
  font-weight: 700;
  margin-bottom: 8px;
  color: var(--accent-blue);
}

.seo-card p {
  font-size: 0.85rem;
  color: var(--text-secondary);
  line-height: 1.5;
}

/* Footer */
.footer {
  text-align: center;
  color: var(--text-secondary);
  font-size: 0.85rem;
  border-top: 1px solid var(--card-border);
  padding-top: 24px;
}