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

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  background: #f0f4f8;
  color: #1a202c;
  line-height: 1.6;
}

.container {
  max-width: 1100px;
  margin: 0 auto;
  padding: 0 20px;
}

header {
  background: linear-gradient(135deg, #2d3748, #4a5568);
  color: white;
  padding: 30px 0;
  text-align: center;
}

header h1 {
  font-size: 2.2rem;
  margin-bottom: 8px;
}

header p {
  opacity: 0.8;
  font-size: 1.05rem;
}

main {
  padding: 30px 0;
}

/* Tabs */
.tabs {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-bottom: 30px;
  border-bottom: 2px solid #e2e8f0;
  padding-bottom: 12px;
}

.tab-btn {
  padding: 10px 20px;
  border: none;
  background: transparent;
  cursor: pointer;
  font-size: 0.95rem;
  font-weight: 600;
  color: #718096;
  border-radius: 8px;
  transition: all 0.2s;
}

.tab-btn:hover {
  background: #edf2f7;
  color: #2d3748;
}

.tab-btn.active {
  background: #2d3748;
  color: white;
}

/* Tab Content */
.tab-content {
  display: none;
  animation: fadeIn 0.3s ease;
}

.tab-content.active {
  display: block;
}

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

h2 {
  font-size: 1.6rem;
  margin-bottom: 6px;
  color: #2d3748;
}

.desc {
  color: #718096;
  margin-bottom: 20px;
  font-size: 0.95rem;
}

/* Forms */
.form-group {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  margin-bottom: 20px;
}

.form-group input,
.form-group select,
.form-group textarea {
  flex: 1;
  min-width: 200px;
  padding: 10px 14px;
  border: 2px solid #e2e8f0;
  border-radius: 8px;
  font-size: 0.95rem;
  transition: border-color 0.2s;
  background: white;
}

.form-group input:focus,
.form-group select:focus,
.form-group textarea:focus {
  outline: none;
  border-color: #4a5568;
}

.form-group textarea {
  resize: vertical;
  font-family: inherit;
}

.form-group button {
  padding: 10px 28px;
  background: #2d3748;
  color: white;
  border: none;
  border-radius: 8px;
  font-size: 0.95rem;
  font-weight: 600;
  cursor: pointer;
  transition: background 0.2s;
  white-space: nowrap;
}

.form-group button:hover {
  background: #1a202c;
}

.form-group button:disabled {
  opacity: 0.6;
  cursor: not-allowed;
}

.form-group label {
  display: flex;
  align-items: center;
  gap: 10px;
  font-weight: 500;
}

.form-group input[type="range"] {
  flex: none;
  width: 150px;
  min-width: auto;
}

/* Results */
.results-box {
  background: white;
  border-radius: 12px;
  padding: 20px;
  box-shadow: 0 2px 8px rgba(0,0,0,0.06);
  margin-top: 12px;
  min-height: 60px;
  border: 1px solid #e2e8f0;
}

.results-box pre {
  background: #f7fafc;
  padding: 16px;
  border-radius: 8px;
  overflow-x: auto;
  font-size: 0.85rem;
  white-space: pre-wrap;
  word-break: break-all;
}

.results-box .keyword-list {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

.results-box .keyword-tag {
  background: #edf2f7;
  padding: 4px 14px;
  border-radius: 20px;
  font-size: 0.85rem;
  color: #2d3748;
}

.results-box .keyword-tag:hover {
  background: #e2e8f0;
}

.preview-box {
  margin-top: 16px;
  padding: 16px;
  background: #f7fafc;
  border-radius: 8px;
  border-left: 4px solid #4a5568;
}

.preview-box h3 {
  color: #2d3748;
  margin-bottom: 6px;
}

.preview-box .preview-url {
  color: #718096;
  font-size: 0.9rem;
}

.preview-box .preview-desc {
  color: #4a5568;
  margin-top: 4px;
}

.speed-scores {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
  gap: 16px;
  margin: 12px 0;
}

.speed-scores .score-item {
  text-align: center;
  padding: 12px;
  background: #f7fafc;
  border-radius: 8px;
}

.speed-scores .score-item .score-value {
  font-size: 2rem;
  font-weight: 700;
  display: block;
}

.speed-scores .score-item .score-label {
  font-size: 0.85rem;
  color: #718096;
}

.score-good { color: #38a169; }
.score-avg { color: #d69e2e; }
.score-poor { color: #e53e3e; }

.image-compare {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 20px;
  margin: 12px 0;
}

.image-compare .compare-item {
  text-align: center;
}

.image-compare .compare-item img {
  max-width: 100%;
  max-height: 300px;
  border-radius: 8px;
  border: 1px solid #e2e8f0;
}

/* Loading */
.loading {
  display: none;
  padding: 20px;
  text-align: center;
  color: #718096;
  font-size: 1rem;
}

.loading.active {
  display: block;
}

/* Footer */
footer {
  background: #2d3748;
  color: #a0aec0;
  text-align: center;
  padding: 20px 0;
  margin-top: 30px;
  font-size: 0.9rem;
}

/* Responsive */
@media (max-width: 768px) {
  .tabs {
    flex-direction: column;
  }
  .tab-btn {
    width: 100%;
    text-align: center;
  }
  .form-group {
    flex-direction: column;
  }
  .form-group input,
  .form-group select,
  .form-group textarea {
    min-width: 100%;
  }
  .image-compare {
    grid-template-columns: 1fr;
  }
  header h1 {
    font-size: 1.6rem;
  }
}

.btn-secondary {
  padding: 8px 20px;
  background: #e2e8f0;
  color: #2d3748;
  border: none;
  border-radius: 6px;
  font-size: 0.9rem;
  cursor: pointer;
  margin-top: 12px;
  transition: background 0.2s;
}

.btn-secondary:hover {
  background: #cbd5e0;
}