/*
 * 星火AI家教 — tutor.spark1.cn 落地页样式
 * 教育蓝 #3b82f6 + 成长绿 #10b981
 */

:root {
    --c-primary: #3b82f6;
    --c-secondary: #10b981;
    --c-accent: #f59e0b;
    --c-accent-warm: #ef4444;
    --c-glow: rgba(59, 130, 246, 0.35);
    --grad-text: linear-gradient(135deg, #60a5fa 0%, #34d399 50%, #fbbf24 100%);
    --grad-btn: linear-gradient(135deg, #3b82f6 0%, #10b981 100%);
    --grad-card-border: linear-gradient(135deg, rgba(59,130,246,0.5), rgba(16,185,129,0.5), rgba(245,158,11,0.5));
    --shadow-glow: 0 0 30px var(--c-glow);
    --shadow-btn: 0 4px 15px rgba(59,130,246,0.4);
}

/* Hero 区 */
.hero h1 {
    background: linear-gradient(135deg, #93c5fd 0%, #6ee7b7 40%, #fde68a 70%, #60a5fa 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

/* 学段选择器 */
.stage-selector {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    gap: 10px;
    margin: 2rem auto;
    max-width: 800px;
}

.stage-btn {
    padding: 10px 20px;
    border: 2px solid rgba(59, 130, 246, 0.3);
    border-radius: 25px;
    background: rgba(59, 130, 246, 0.08);
    color: #93c5fd;
    font-size: 0.95rem;
    cursor: pointer;
    transition: all 0.3s;
    white-space: nowrap;
}

.stage-btn:hover {
    border-color: var(--c-primary);
    background: rgba(59, 130, 246, 0.15);
    color: #bfdbfe;
    transform: translateY(-2px);
}

.stage-btn.active {
    background: var(--grad-btn);
    border-color: transparent;
    color: white;
    font-weight: 600;
    box-shadow: var(--shadow-btn);
}

/* 学科卡片网格 */
.subjects-section {
    padding: 3rem 0;
}

.subjects-section h2 {
    text-align: center;
    font-size: 1.8rem;
    margin-bottom: 0.5rem;
    color: #e2e8f0;
}

.subjects-section .section-desc {
    text-align: center;
    color: #94a3b8;
    margin-bottom: 2rem;
    font-size: 1rem;
}

.subjects-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
    gap: 1.2rem;
    max-width: 1100px;
    margin: 0 auto;
}

.subject-card {
    background: rgba(30, 41, 59, 0.7);
    border: 1px solid rgba(59, 130, 246, 0.15);
    border-radius: 16px;
    padding: 1.5rem;
    cursor: pointer;
    transition: all 0.3s;
    position: relative;
    overflow: hidden;
    text-decoration: none;
    display: block;
    color: inherit;
}

.subject-card::before {
    content: '';
    position: absolute;
    top: 0; left: 0; right: 0;
    height: 3px;
    background: var(--grad-btn);
    opacity: 0;
    transition: opacity 0.3s;
}

.subject-card:hover {
    border-color: rgba(59, 130, 246, 0.4);
    transform: translateY(-4px);
    box-shadow: 0 8px 30px rgba(59, 130, 246, 0.15);
}

.subject-card:hover::before {
    opacity: 1;
}

.subject-card .card-icon {
    font-size: 2.5rem;
    margin-bottom: 0.8rem;
    display: block;
}

.subject-card .card-title {
    font-size: 1.2rem;
    font-weight: 700;
    color: #e2e8f0;
    margin-bottom: 0.5rem;
}

.subject-card .card-desc {
    font-size: 0.88rem;
    color: #94a3b8;
    line-height: 1.6;
    margin-bottom: 0.8rem;
}

.subject-card .card-meta {
    display: flex;
    align-items: center;
    gap: 8px;
    flex-wrap: wrap;
}

.card-cost {
    display: inline-block;
    padding: 3px 10px;
    background: rgba(245, 158, 11, 0.12);
    color: #fbbf24;
    border-radius: 12px;
    font-size: 0.8rem;
    font-weight: 600;
}

.card-free {
    display: inline-block;
    padding: 3px 10px;
    background: rgba(16, 185, 129, 0.12);
    color: #34d399;
    border-radius: 12px;
    font-size: 0.8rem;
    font-weight: 600;
}

.card-stages {
    display: inline-block;
    padding: 3px 10px;
    background: rgba(59, 130, 246, 0.1);
    color: #93c5fd;
    border-radius: 12px;
    font-size: 0.75rem;
}

/* 对比优势区 */
.advantages {
    padding: 4rem 0;
}

.advantages h2 {
    text-align: center;
    font-size: 1.8rem;
    color: #e2e8f0;
    margin-bottom: 2rem;
}

.adv-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
    gap: 1.5rem;
    max-width: 1000px;
    margin: 0 auto;
}

.adv-card {
    background: rgba(30, 41, 59, 0.6);
    border: 1px solid rgba(59, 130, 246, 0.12);
    border-radius: 16px;
    padding: 2rem 1.5rem;
    text-align: center;
    transition: all 0.3s;
}

.adv-card:hover {
    border-color: rgba(59, 130, 246, 0.3);
    transform: translateY(-3px);
}

.adv-card .adv-icon {
    font-size: 2.5rem;
    margin-bottom: 1rem;
    display: block;
}

.adv-card h3 {
    font-size: 1.1rem;
    color: #e2e8f0;
    margin-bottom: 0.5rem;
}

.adv-card p {
    font-size: 0.9rem;
    color: #94a3b8;
    line-height: 1.7;
}

/* 学习阶段时间轴 */
.timeline-section {
    padding: 4rem 0;
    text-align: center;
}

.timeline-section h2 {
    font-size: 1.8rem;
    color: #e2e8f0;
    margin-bottom: 2rem;
}

.timeline {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    gap: 0;
    max-width: 900px;
    margin: 0 auto;
    position: relative;
}

.timeline::before {
    content: '';
    position: absolute;
    top: 50%;
    left: 5%;
    right: 5%;
    height: 2px;
    background: linear-gradient(90deg, rgba(59,130,246,0.1), rgba(59,130,246,0.4), rgba(16,185,129,0.4), rgba(16,185,129,0.1));
    z-index: 0;
}

.timeline-item {
    position: relative;
    z-index: 1;
    padding: 10px 14px;
    background: rgba(30, 41, 59, 0.9);
    border: 1px solid rgba(59, 130, 246, 0.2);
    border-radius: 20px;
    font-size: 0.85rem;
    color: #93c5fd;
    white-space: nowrap;
    transition: all 0.3s;
    cursor: default;
}

.timeline-item:hover {
    border-color: var(--c-primary);
    color: #bfdbfe;
    transform: scale(1.05);
}

.timeline-item .tl-icon {
    margin-right: 4px;
}

/* FAQ */
.tutor-faq {
    padding: 3rem 0;
    max-width: 800px;
    margin: 0 auto;
}

.tutor-faq h2 {
    text-align: center;
    font-size: 1.8rem;
    color: #e2e8f0;
    margin-bottom: 2rem;
}

.tutor-faq details {
    background: rgba(30, 41, 59, 0.5);
    border: 1px solid rgba(59, 130, 246, 0.12);
    border-radius: 12px;
    margin-bottom: 12px;
    overflow: hidden;
}

.tutor-faq summary {
    padding: 16px 20px;
    cursor: pointer;
    font-weight: 600;
    color: #e2e8f0;
    font-size: 1rem;
    transition: background 0.2s;
}

.tutor-faq summary:hover {
    background: rgba(59, 130, 246, 0.06);
}

.tutor-faq details[open] summary {
    border-bottom: 1px solid rgba(59, 130, 246, 0.12);
}

.tutor-faq details p {
    padding: 16px 20px;
    color: #94a3b8;
    line-height: 1.8;
    font-size: 0.95rem;
}

/* CTA 区 */
.tutor-cta {
    text-align: center;
    padding: 4rem 0;
}

.tutor-cta .cta-title {
    font-size: 1.6rem;
    color: #e2e8f0;
    margin-bottom: 1rem;
}

.tutor-cta .cta-desc {
    color: #94a3b8;
    margin-bottom: 2rem;
    font-size: 1rem;
}

.tutor-cta .cta-btn {
    display: inline-block;
    padding: 14px 40px;
    background: var(--grad-btn);
    color: white;
    font-size: 1.1rem;
    font-weight: 700;
    border-radius: 30px;
    text-decoration: none;
    box-shadow: var(--shadow-btn);
    transition: all 0.3s;
}

.tutor-cta .cta-btn:hover {
    transform: translateY(-3px);
    box-shadow: 0 8px 25px rgba(59, 130, 246, 0.5);
}

/* 空状态（老年等无学科导师的学段） */
.empty-stage {
    text-align: center;
    padding: 3rem 1rem;
    color: #94a3b8;
}

.empty-stage .empty-icon {
    font-size: 3rem;
    margin-bottom: 1rem;
    display: block;
}

.empty-stage h3 {
    color: #e2e8f0;
    margin-bottom: 0.5rem;
}

.empty-stage .empty-links {
    margin-top: 1.5rem;
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    gap: 12px;
}

.empty-stage .empty-links a {
    display: inline-block;
    padding: 10px 20px;
    background: rgba(59, 130, 246, 0.1);
    border: 1px solid rgba(59, 130, 246, 0.2);
    border-radius: 12px;
    color: #93c5fd;
    text-decoration: none;
    font-size: 0.9rem;
    transition: all 0.3s;
}

.empty-stage .empty-links a:hover {
    background: rgba(59, 130, 246, 0.2);
    border-color: rgba(59, 130, 246, 0.4);
}

/* 响应式 */
@media (max-width: 768px) {
    .hero h1 { font-size: 1.8rem; }
    .stage-selector { gap: 8px; }
    .stage-btn { padding: 8px 14px; font-size: 0.85rem; }
    .subjects-grid { grid-template-columns: 1fr; }
    .adv-grid { grid-template-columns: 1fr 1fr; }
    .timeline { gap: 8px; }
    .timeline-item { font-size: 0.75rem; padding: 6px 10px; }
}

@media (max-width: 480px) {
    .adv-grid { grid-template-columns: 1fr; }
    .hero h1 { font-size: 1.5rem; }
}