/* Reset and Base Styles */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    background-color: #FAFAFA;
    color: #1A1A1A;
    line-height: 1.6;
}

/* Color Variables */
:root {
    --primary-teal: #0D6E6E;
    --secondary-orange: #E07B54;
    --bg-primary: #FAFAFA;
    --bg-surface: #FFFFFF;
    --bg-muted: #F5F5F5;
    --text-primary: #1A1A1A;
    --text-secondary: #666666;
    --text-tertiary: #888888;
    --border-primary: #E5E5E5;
    --border-divider: #F0F0F0;
}

/* Header */
.header {
    background: var(--bg-surface);
    border-bottom: 1px solid var(--border-primary);
    position: sticky;
    top: 0;
    z-index: 100;
}

.header-content {
    max-width: 1440px;
    margin: 0 auto;
    padding: 0 80px;
    height: 72px;
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.logo {
    display: flex;
    align-items: center;
    gap: 12px;
}

.logo-icon {
    width: 36px;
    height: 36px;
    background: var(--primary-teal);
    border-radius: 8px;
}

.logo-icon.small {
    width: 32px;
    height: 32px;
}

.logo-text {
    font-size: 22px;
    font-weight: 600;
    color: var(--text-primary);
}

.nav {
    display: flex;
    gap: 32px;
}

.nav-item {
    font-size: 15px;
    font-weight: 500;
    color: var(--text-secondary);
    text-decoration: none;
    transition: color 0.2s;
}

.nav-item:hover,
.nav-item.active {
    color: var(--primary-teal);
}

.header-right {
    display: flex;
    align-items: center;
    gap: 16px;
}

.login-btn {
    font-size: 15px;
    font-weight: 500;
    color: var(--text-secondary);
    text-decoration: none;
}

.start-btn {
    padding: 10px 24px;
    background: var(--primary-teal);
    color: white;
    border: none;
    border-radius: 8px;
    font-size: 15px;
    font-weight: 600;
    cursor: pointer;
    transition: background 0.2s;
}

.start-btn:hover {
    background: #0a5a5a;
}

/* Hero Section */
.hero {
    background: var(--bg-surface);
    padding: 80px 120px;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 32px;
}

.hero-title {
    font-size: 48px;
    font-weight: 700;
    color: var(--text-primary);
    text-align: center;
}

.hero-subtitle {
    font-size: 18px;
    color: var(--text-secondary);
    text-align: center;
    max-width: 600px;
}

/* Upload Area */
.upload-area {
    width: 680px;
    padding: 48px;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 24px;
    background: var(--bg-primary);
    border: 2px dashed var(--border-primary);
    border-radius: 16px;
    cursor: pointer;
    transition: border-color 0.2s, background 0.2s;
}

.upload-area:hover,
.upload-area.dragover {
    border-color: var(--primary-teal);
    background: #f0f9f9;
}

.upload-icon {
    font-size: 64px;
    color: var(--primary-teal);
}

.upload-title {
    font-size: 18px;
    font-weight: 500;
    color: var(--text-primary);
}

.upload-hint {
    font-size: 14px;
    color: var(--text-tertiary);
}

.upload-buttons {
    display: flex;
    gap: 16px;
}

.upload-btn {
    display: flex;
    align-items: center;
    gap: 8px;
    padding: 14px 32px;
    border-radius: 8px;
    font-size: 16px;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.2s;
    border: none;
}

.upload-btn.primary {
    background: var(--primary-teal);
    color: white;
    font-weight: 600;
}

.upload-btn.primary:hover {
    background: #0a5a5a;
}

.upload-btn.secondary {
    background: var(--bg-surface);
    color: var(--text-primary);
    border: 1px solid var(--border-primary);
}

.upload-btn.secondary:hover {
    border-color: var(--primary-teal);
    color: var(--primary-teal);
}

.upload-btn i {
    font-size: 20px;
}

/* Processing Status */
.processing-status {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 16px;
    padding: 40px;
}

.processing-spinner {
    width: 48px;
    height: 48px;
    border: 4px solid var(--border-primary);
    border-top-color: var(--primary-teal);
    border-radius: 50%;
    animation: spin 1s linear infinite;
}

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

.processing-text {
    font-size: 16px;
    color: var(--text-secondary);
}

/* Preview Section */
.preview-section {
    background: var(--bg-muted);
    padding: 80px 80px;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 48px;
}

.preview-header {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 16px;
}

.preview-badge,
.features-badge,
.steps-badge {
    padding: 6px 16px;
    background: #E8F5F5;
    border-radius: 20px;
    font-size: 13px;
    font-weight: 600;
    color: var(--primary-teal);
}

.preview-title,
.features-title,
.steps-title {
    font-size: 36px;
    font-weight: 700;
    color: var(--text-primary);
}

.preview-subtitle,
.features-subtitle {
    font-size: 16px;
    color: var(--text-secondary);
}

/* Preview Container */
.preview-container {
    width: 100%;
    max-width: 1200px;
    display: flex;
    gap: 32px;
}

.slide-nav {
    width: 200px;
    flex-shrink: 0;
    display: flex;
    flex-direction: column;
    gap: 12px;
}

.slide-nav-title {
    font-size: 14px;
    font-weight: 600;
    color: var(--text-tertiary);
}

.slide-nav-list {
    display: flex;
    flex-direction: column;
    gap: 8px;
}

.slide-nav-item {
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 12px 16px;
    background: var(--bg-surface);
    border: 1px solid var(--border-primary);
    border-radius: 8px;
    cursor: pointer;
    transition: all 0.2s;
}

.slide-nav-item:hover {
    border-color: var(--primary-teal);
}

.slide-nav-item.active {
    background: var(--primary-teal);
    border-color: var(--primary-teal);
}

.slide-nav-item .num {
    font-size: 14px;
    font-weight: 700;
    font-family: 'JetBrains Mono', monospace;
    color: var(--text-tertiary);
}

.slide-nav-item.active .num {
    color: white;
}

.slide-nav-item .text {
    font-size: 14px;
    font-weight: 500;
    color: var(--text-secondary);
}

.slide-nav-item.active .text {
    color: white;
}

/* Slide Preview */
.slide-preview {
    width: 900px;
    height: 506px; /* 900 / 16 * 9 = 506.25 */
    flex-shrink: 0;
    background: var(--bg-surface);
    border: 1px solid var(--border-primary);
    border-radius: 12px;
    overflow: hidden;
    display: flex;
    flex-direction: column;
    box-shadow: 0 4px 20px rgba(0, 0, 0, 0.1);
}

.slide-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 0 24px;
    height: 56px;
    background: var(--primary-teal);
}

.slide-header-left {
    display: flex;
    align-items: center;
    gap: 12px;
}

.slide-num-badge {
    padding: 4px 12px;
    background: rgba(255, 255, 255, 0.2);
    border-radius: 4px;
    font-size: 14px;
    font-weight: 600;
    color: white;
}

.slide-type {
    font-size: 14px;
    font-weight: 500;
    color: white;
}

.slide-header-right {
    display: flex;
    gap: 8px;
}

.diff-badge {
    padding: 4px 10px;
    background: var(--secondary-orange);
    border-radius: 4px;
    font-size: 12px;
    font-weight: 600;
    color: white;
}

.score-badge {
    padding: 4px 10px;
    background: rgba(255, 255, 255, 0.2);
    border-radius: 4px;
    font-size: 12px;
    font-weight: 600;
    color: white;
}

.slide-content {
    display: flex;
    padding: 24px;
    gap: 24px;
    flex: 1;
    overflow: auto;
}

.slide-left,
.slide-right {
    flex: 1;
    display: flex;
    flex-direction: column;
    gap: 20px;
}

/* Question Section */
.question-section,
.analysis-section,
.knowledge-section {
    display: flex;
    flex-direction: column;
    gap: 12px;
}

.section-label {
    display: flex;
    align-items: center;
    gap: 8px;
}

.section-label i {
    font-size: 18px;
    color: var(--primary-teal);
}

.section-label.orange i {
    color: var(--secondary-orange);
}

.section-label span {
    font-size: 14px;
    font-weight: 600;
    color: var(--primary-teal);
}

.section-label.orange span {
    color: var(--secondary-orange);
}

.question-text {
    font-size: 15px;
    color: var(--text-primary);
    line-height: 1.6;
}

/* Options */
.options-list {
    display: flex;
    flex-direction: column;
    gap: 10px;
}

.option-item {
    display: flex;
    align-items: center;
    gap: 10px;
    padding: 10px 14px;
    background: var(--bg-muted);
    border-radius: 8px;
}

.option-item.correct {
    background: #E8F5F5;
    border: 2px solid var(--primary-teal);
}

.option-item .letter {
    font-size: 14px;
    font-weight: 700;
    font-family: 'JetBrains Mono', monospace;
    color: var(--text-tertiary);
}

.option-item.correct .letter {
    color: var(--primary-teal);
}

.option-item .text {
    font-size: 14px;
    color: var(--text-secondary);
}

.option-item.correct .text {
    color: var(--primary-teal);
    font-weight: 500;
}

.option-item.correct i {
    color: var(--primary-teal);
    margin-right: 4px;
}

/* Analysis Section */
.analysis-box {
    padding: 16px;
    background: var(--bg-primary);
    border-radius: 12px;
}

.analysis-text {
    font-size: 13px;
    color: var(--text-secondary);
    line-height: 1.7;
    white-space: pre-line;
}

/* Knowledge Tags */
.knowledge-tags {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
}

.knowledge-tag {
    padding: 6px 12px;
    background: #E8F5F5;
    border-radius: 16px;
    font-size: 12px;
    font-weight: 500;
    color: var(--primary-teal);
}

/* Answer Box for Fill-in-the-blank */
.answer-box {
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 14px 18px;
    background: #E8F5F5;
    border: 2px solid var(--primary-teal);
    border-radius: 8px;
}

.answer-label {
    font-size: 14px;
    font-weight: 600;
    color: var(--primary-teal);
}

.answer-value {
    font-size: 16px;
    font-weight: 700;
    color: var(--primary-teal);
    font-family: 'JetBrains Mono', monospace;
}

/* Lucide Icons */
[class^="lucide-"],
[class*=" lucide-"] {
    display: inline-flex;
    align-items: center;
    justify-content: center;
}

/* Action Buttons */
.action-buttons {
    display: flex;
    align-items: center;
    gap: 16px;
}

.action-btn {
    display: flex;
    align-items: center;
    gap: 10px;
    padding: 14px 32px;
    border-radius: 8px;
    font-size: 16px;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s;
    border: none;
}

.action-btn.primary {
    background: var(--primary-teal);
    color: white;
}

.action-btn.primary:hover {
    background: #0a5a5a;
}

.action-btn.secondary {
    background: var(--bg-surface);
    color: var(--text-primary);
    border: 1px solid var(--border-primary);
    font-weight: 500;
}

.action-btn.secondary:hover {
    border-color: var(--primary-teal);
    color: var(--primary-teal);
}

.action-btn i {
    font-size: 20px;
}

.slide-count {
    font-size: 14px;
    color: var(--text-tertiary);
}

/* Features Section */
.features-section {
    background: var(--bg-surface);
    padding: 80px 120px;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 48px;
}

.features-header,
.steps-header {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 16px;
}

.features-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 24px;
    width: 100%;
    max-width: 1200px;
}

.feature-card {
    padding: 28px;
    background: var(--bg-primary);
    border-radius: 16px;
    display: flex;
    flex-direction: column;
    gap: 16px;
}

.feature-icon {
    width: 48px;
    height: 48px;
    border-radius: 12px;
    display: flex;
    align-items: center;
    justify-content: center;
}

.feature-icon.teal {
    background: var(--primary-teal);
}

.feature-icon.orange {
    background: var(--secondary-orange);
}

.feature-icon i {
    font-size: 24px;
    color: white;
}

.feature-title {
    font-size: 20px;
    font-weight: 600;
    color: var(--text-primary);
}

.feature-desc {
    font-size: 14px;
    color: var(--text-secondary);
    line-height: 1.6;
}

/* Steps Section */
.steps-section {
    background: var(--bg-muted);
    padding: 80px 120px;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 48px;
}

.steps-grid {
    display: flex;
    gap: 32px;
    justify-content: center;
}

.step-card {
    width: 320px;
    padding: 32px;
    background: var(--bg-surface);
    border: 1px solid var(--border-primary);
    border-radius: 16px;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 20px;
}

.step-num {
    width: 56px;
    height: 56px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 24px;
    font-weight: 700;
    font-family: 'JetBrains Mono', monospace;
    color: white;
}

.step-num.teal {
    background: var(--primary-teal);
}

.step-num.orange {
    background: var(--secondary-orange);
}

.step-title {
    font-size: 20px;
    font-weight: 600;
    color: var(--text-primary);
}

.step-desc {
    font-size: 14px;
    color: var(--text-secondary);
    text-align: center;
    line-height: 1.5;
}

/* Footer */
.footer {
    background: #1A1A1A;
    padding: 48px 120px;
}

.footer-content {
    max-width: 1200px;
    margin: 0 auto;
}

.footer-top {
    display: flex;
    justify-content: space-between;
    margin-bottom: 32px;
}

.footer-brand {
    display: flex;
    flex-direction: column;
    gap: 16px;
}

.footer-logo {
    display: flex;
    align-items: center;
    gap: 12px;
}

.footer-logo .logo-text {
    color: white;
    font-size: 20px;
}

.footer-slogan {
    font-size: 14px;
    color: #888888;
}

.footer-links {
    display: flex;
    gap: 64px;
}

.link-column {
    display: flex;
    flex-direction: column;
    gap: 16px;
}

.link-column h4 {
    font-size: 14px;
    font-weight: 600;
    color: white;
}

.link-column a {
    font-size: 14px;
    color: #888888;
    text-decoration: none;
    transition: color 0.2s;
}

.link-column a:hover {
    color: white;
}

.footer-divider {
    height: 1px;
    background: #333333;
    margin-bottom: 32px;
}

.footer-bottom {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.copyright {
    font-size: 13px;
    color: #666666;
}

.social-icons {
    display: flex;
    gap: 16px;
}

.social-icons i {
    font-size: 20px;
    color: #666666;
    cursor: pointer;
    transition: color 0.2s;
}

.social-icons i:hover {
    color: white;
}

/* Responsive */
@media (max-width: 1200px) {
    .features-grid {
        grid-template-columns: repeat(2, 1fr);
    }

    .steps-grid {
        flex-wrap: wrap;
    }
}

@media (max-width: 768px) {
    .header-content {
        padding: 0 24px;
    }

    .nav {
        display: none;
    }

    .hero {
        padding: 40px 24px;
    }

    .hero-title {
        font-size: 32px;
    }

    .upload-area {
        width: 100%;
        padding: 32px 24px;
    }

    .preview-container {
        flex-direction: column;
    }

    .slide-nav {
        width: 100%;
        flex-direction: row;
        overflow-x: auto;
    }

    .slide-nav-list {
        flex-direction: row;
    }

    .slide-content {
        flex-direction: column;
    }

    .slide-preview {
        width: 100%;
        height: auto;
        aspect-ratio: 16 / 9;
    }

    .features-grid {
        grid-template-columns: 1fr;
    }

    .steps-grid {
        flex-direction: column;
        align-items: center;
    }

    .footer-top {
        flex-direction: column;
        gap: 32px;
    }

    .footer-links {
        flex-wrap: wrap;
        gap: 32px;
    }
}