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

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Microsoft YaHei', sans-serif;
    background: linear-gradient(135deg, #FFB6C1 0%, #87CEEB 30%, #98FB98 60%, #F0E68C 100%);
    min-height: 100vh;
    padding: 20px;
    position: relative;
    overflow-x: hidden;
}

/* 背景装饰 */
body::before {
    content: '';
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-image:
        radial-gradient(circle at 20% 80%, rgba(255,255,255,0.3) 0%, transparent 50%),
        radial-gradient(circle at 80% 20%, rgba(255,255,255,0.2) 0%, transparent 50%),
        radial-gradient(circle at 40% 40%, rgba(255,255,255,0.1) 0%, transparent 50%);
    pointer-events: none;
    z-index: 1;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    position: relative;
    z-index: 2;
}

/* 头部 */
.header {
    text-align: center;
    margin-bottom: 40px;
    animation: fadeInDown 0.8s ease;
}

.logo {
    font-size: 3.5rem;
    font-weight: 800;
    background: linear-gradient(45deg, #FF6B6B, #4ECDC4, #45B7D1, #96CEB4);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    margin-bottom: 10px;
    text-shadow: 2px 2px 4px rgba(0,0,0,0.1);
}

.subtitle {
    font-size: 1.2rem;
    color: #666;
    margin-bottom: 20px;
}

.welcome-card {
    background: linear-gradient(135deg, rgba(255,255,255,0.9) 0%, rgba(255,255,255,0.7) 100%);
    border-radius: 25px;
    padding: 30px;
    box-shadow: 0 15px 35px rgba(0,0,0,0.1);
    backdrop-filter: blur(10px);
    border: 2px solid rgba(255,255,255,0.3);
    margin-bottom: 40px;
}

/* 选择区域 */
.selection-area {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 30px;
    margin-bottom: 40px;
}

.selection-card {
    background: linear-gradient(135deg, rgba(255,255,255,0.95) 0%, rgba(255,255,255,0.85) 100%);
    border-radius: 20px;
    padding: 25px;
    box-shadow: 0 10px 30px rgba(0,0,0,0.1);
    backdrop-filter: blur(15px);
    border: 2px solid rgba(255,255,255,0.4);
    transition: all 0.3s ease;
    animation: fadeInUp 0.8s ease;
}

.selection-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 15px 40px rgba(0,0,0,0.15);
}

.card-title {
    font-size: 1.5rem;
    font-weight: 700;
    margin-bottom: 20px;
    text-align: center;
    color: #333;
}

.card-title .emoji {
    font-size: 2rem;
    margin-right: 10px;
}

/* 选择按钮样式 */
.select-btn {
    width: 100%;
    padding: 20px;
    border: none;
    border-radius: 15px;
    font-size: 1.2rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
    background: linear-gradient(135deg, #E0F6FF 0%, #E8F5E8 100%);
    color: #333;
    border: 2px solid rgba(78,205,196,0.3);
    display: flex;
    align-items: center;
    justify-content: space-between;
    position: relative;
    overflow: hidden;
}

.select-btn:hover {
    transform: scale(1.02);
    box-shadow: 0 5px 20px rgba(78,205,196,0.3);
    background: linear-gradient(135deg, #4ECDC4 0%, #44A08D 100%);
    color: white;
}

.select-btn .current-selection {
    display: flex;
    align-items: center;
    gap: 10px;
}

.select-btn .arrow {
    font-size: 1.5rem;
    transition: transform 0.3s ease;
}

.select-btn:hover .arrow {
    transform: rotate(180deg);
}

/* 全屏模态框 */
.modal-overlay {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0,0,0,0.8);
    backdrop-filter: blur(10px);
    z-index: 1000;
    display: none;
    align-items: center;
    justify-content: center;
    animation: fadeIn 0.3s ease;
}

  .modal-overlay.show {
    display: flex;
}

 .modal-content {
    background: linear-gradient(135deg, rgba(255,255,255,0.95) 0%, rgba(255,255,255,0.9) 100%);
    border-radius: 25px;
    padding: 40px;
    max-width: 90vw;
    max-height: 90vh;
    overflow-y: auto;
    box-shadow: 0 25px 50px rgba(0,0,0,0.3);
    backdrop-filter: blur(20px);
    border: 3px solid rgba(255,255,255,0.5);
    position: relative;
    animation: slideInUp 0.4s ease;
}

/* 科目选择模态框全屏样式 */
.modal-overlay.full-screen {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 50%, #f093fb 100%);
    backdrop-filter: blur(20px);
}

.modal-overlay.full-screen .modal-content {
    width: 100vw;
    height: 100vh;
    max-width: 100vw;
    max-height: 100vh;
    border-radius: 0;
    padding: 60px 40px;
    background: linear-gradient(135deg, rgba(255,255,255,0.98) 0%, rgba(255,255,255,0.95) 100%);
    border: none;
    display: flex;
    flex-direction: column;
    animation: zoomIn 0.5s ease;
}

.modal-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 30px;
    padding-bottom: 20px;
    border-bottom: 2px solid rgba(78,205,196,0.3);
}

.modal-title {
    font-size: 2rem;
    font-weight: 700;
    color: #333;
    display: flex;
    align-items: center;
    gap: 15px;
}

.close-btn {
    width: 50px;
    height: 50px;
    border: none;
    border-radius: 50%;
    background: linear-gradient(135deg, #FF6B6B 0%, #FF8E8E 100%);
    color: white;
    font-size: 1.5rem;
    cursor: pointer;
    transition: all 0.3s ease;
    display: flex;
    align-items: center;
    justify-content: center;
}

.close-btn:hover {
    transform: scale(1.1);
    box-shadow: 0 5px 15px rgba(255,107,107,0.4);
}

/* 年级选择网格 */
.grade-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 20px;
    margin-bottom: 20px;
}        .grade-option {
    background: linear-gradient(135deg, #FFE4E1 0%, #E6E6FA 100%);
    border: 3px solid transparent;
    border-radius: 20px;
    padding: 20px;
    cursor: pointer;
    transition: all 0.3s ease;
    position: relative;
    overflow: hidden;
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 15px;
}

.grade-option:hover {
    transform: translateY(-5px);
    box-shadow: 0 10px 25px rgba(0,0,0,0.15);
    border-color: #FF6B6B;
}

.grade-option.selected {
    background: linear-gradient(135deg, #FF6B6B 0%, #FF8E8E 100%);
    color: white;
    border-color: #FF6B6B;
    transform: translateY(-5px);
    box-shadow: 0 15px 30px rgba(255,107,107,0.4);
}

.grade-name {
    font-size: 1.3rem;
    font-weight: 700;
    min-width: 90px;
}        .semester-buttons {
    display: flex;
    gap: 10px;
    justify-content: flex-end;
    flex: 1;
}

.semester-btn {
    padding: 10px 20px;
    border: 2px solid rgba(255,255,255,0.3);
    border-radius: 12px;
    background: rgba(255,255,255,0.2);
    color: inherit;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
    min-width: 100px;
    text-align: center;
}

.grade-option:not(.selected) .semester-btn:hover {
    background: rgba(255,107,107,0.3);
    border-color: #FF6B6B;
}

.grade-option.selected .semester-btn.active {
    background: rgba(255,255,255,0.3);
    border-color: rgba(255,255,255,0.6);
    box-shadow: 0 2px 8px rgba(255,255,255,0.2);
}

/* 科目选择网格 */
.subject-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
    gap: 25px;
}

.subject-option {
    background: linear-gradient(135deg, #E0F6FF 0%, #E8F5E8 100%);
    border: 3px solid transparent;
    border-radius: 20px;
    padding: 30px 20px;
    cursor: pointer;
    transition: all 0.3s ease;
    text-align: center;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 15px;
}

.subject-option:hover {
    transform: translateY(-5px);
    box-shadow: 0 10px 25px rgba(0,0,0,0.15);
    border-color: #4ECDC4;
}

.subject-option.selected {
    background: linear-gradient(135deg, #4ECDC4 0%, #44A08D 100%);
    color: white;
    border-color: #4ECDC4;
    transform: translateY(-5px);
    box-shadow: 0 15px 30px rgba(78,205,196,0.4);
}

.subject-emoji {
    font-size: 3rem;
}

.subject-name {
    font-size: 1.2rem;
    font-weight: 700;
}

/* 主题选择 */
.topics-container {
    display: none;
    animation: fadeIn 0.5s ease;
}

.topics-container.show {
    display: block;
}

.topic-card {
    background: linear-gradient(135deg, rgba(255,255,255,0.95) 0%, rgba(255,255,255,0.85) 100%);
    border-radius: 20px;
    padding: 25px;
    margin-bottom: 20px;
    box-shadow: 0 10px 30px rgba(0,0,0,0.1);
    backdrop-filter: blur(15px);
    border: 2px solid rgba(255,255,255,0.4);
    transition: all 0.3s ease;
    cursor: pointer;
}

.topic-card:hover {
    transform: translateY(-3px);
    box-shadow: 0 15px 35px rgba(0,0,0,0.15);
    background: linear-gradient(135deg, rgba(135,206,250,0.3) 0%, rgba(152,251,152,0.3) 100%);
    border-color: #87CEEB;
}

.topic-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 15px;
}

.topic-title {
    font-size: 1.3rem;
    font-weight: 700;
    color: #333;
}

.topic-emoji {
    font-size: 2rem;
}

.topic-description {
    color: #666;
    margin-bottom: 15px;
    line-height: 1.6;
}

.topic-stats {
    display: flex;
    gap: 20px;
    font-size: 0.9rem;
    color: #888;
}

.stat-item {
    display: flex;
    align-items: center;
    gap: 5px;
}

.developing {
    opacity: 0.7;
}

.developing:hover {
    background: linear-gradient(135deg, rgba(200, 200, 200, 0.3) 0%, rgba(150, 150, 150, 0.3) 100%);
    border-color: #ccc;
    cursor: not-allowed;
}

.empty-state {
    text-align: center;
    color: #666;
    padding: 40px 20px;
    font-size: 1.1rem;
}

.empty-state .emoji {
    font-size: 3rem;
    margin-bottom: 15px;
    display: block;
}

@keyframes fadeInDown {
    from {
        opacity: 0;
        transform: translateY(-30px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(30px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

@keyframes fadeIn {
    from { opacity: 0; }
    to { opacity: 1; }
}

@keyframes slideInUp {
    from {
        opacity: 0;
        transform: translateY(50px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

/* 响应式设计 */        @media (max-width: 768px) {
    .container {
        padding: 0 10px;
    }

    .logo {
        font-size: 2.5rem;
    }

    .selection-area {
        grid-template-columns: 1fr;
        gap: 20px;
    }

    .welcome-card {
        padding: 20px;
    }

    .modal-content {
        padding: 25px;
        max-width: 95vw;
        max-height: 95vh;
    }

    .modal-title {
        font-size: 1.5rem;
    }

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

    .grade-option {
        flex-direction: column;
        align-items: center;
        text-align: center;
        gap: 10px;
        padding: 15px;
    }

    .semester-buttons {
        justify-content: center;
    }

    .semester-btn {
        padding: 8px 15px;
        min-width: 80px;
        font-size: 0.9rem;
    }

    .subject-grid {
        grid-template-columns: repeat(2, 1fr);
    }
}

@media (max-width: 480px) {
    body {
        padding: 10px;
    }

    .logo {
        font-size: 2rem;
    }

    .selection-card {
        padding: 20px;
    }

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