:root {
    --primary-color: #4a90e2;
    --secondary-color: #50c878;
    --accent-color: #f5a623;
    --bg-color: #f8fafc;
    --card-bg: #ffffff;
    --text-color: #2c3e50;
    --text-light: #7f8c8d;
    --border-color: #e1e8ed;
    --shadow: 0 4px 15px rgba(0, 0, 0, 0.08);
    --shadow-hover: 0 8px 30px rgba(0, 0, 0, 0.12);
    --radius: 16px;
}

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

body {
    font-family: 'PingFang SC', 'Microsoft YaHei', -apple-system, BlinkMacSystemFont, sans-serif;
    background: var(--bg-color);
    color: var(--text-color);
    line-height: 1.6;
    min-height: 100vh;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
}

.hero {
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    color: white;
    padding: 80px 0;
    text-align: center;
    margin-bottom: 50px;
}

.hero h1 {
    font-size: 3rem;
    margin-bottom: 20px;
    font-weight: 700;
}

.hero p {
    font-size: 1.25rem;
    opacity: 0.95;
}

.card {
    background: var(--card-bg);
    border-radius: var(--radius);
    padding: 30px;
    box-shadow: var(--shadow);
    transition: all 0.3s ease;
    border: 1px solid var(--border-color);
}

.card:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-hover);
}

.scenario-card {
    cursor: pointer;
    text-align: center;
    padding: 40px 30px;
}

.scenario-card:hover {
    border-color: var(--primary-color);
}

.scenario-icon {
    font-size: 4rem;
    margin-bottom: 20px;
}

.scenario-title {
    font-size: 1.5rem;
    color: var(--text-color);
    margin-bottom: 15px;
    font-weight: 600;
}

.scenario-desc {
    color: var(--text-light);
    margin-bottom: 20px;
    line-height: 1.8;
}

.difficulty-badge {
    display: inline-block;
    padding: 8px 20px;
    border-radius: 20px;
    font-size: 0.9rem;
    font-weight: 500;
}

.badge-easy {
    background: #e8f5e9;
    color: #4caf50;
}

.badge-medium {
    background: #fff3e0;
    color: #ff9800;
}

.badge-hard {
    background: #fce4ec;
    color: #e91e63;
}

.input-group {
    text-align: center;
    margin-bottom: 40px;
}

.input-group label {
    display: block;
    font-size: 1.2rem;
    color: var(--text-color);
    margin-bottom: 15px;
    font-weight: 500;
}

.input-group input {
    padding: 14px 28px;
    font-size: 1.1rem;
    border: 2px solid var(--border-color);
    border-radius: 12px;
    width: 100%;
    max-width: 400px;
    text-align: center;
    transition: all 0.3s;
}

.input-group input:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 4px rgba(74, 144, 226, 0.1);
}

.guide-section {
    background: var(--card-bg);
    border-radius: var(--radius);
    padding: 40px;
    margin-top: 50px;
    box-shadow: var(--shadow);
}

.guide-section h2 {
    color: var(--primary-color);
    margin-bottom: 25px;
    font-size: 1.8rem;
}

.guide-section ol {
    list-style-position: inside;
    line-height: 2.2;
    color: var(--text-light);
}

.guide-section li {
    margin-bottom: 12px;
    font-size: 1.1rem;
}

.guide-section strong {
    color: var(--primary-color);
}

.loading-overlay {
    display: none;
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(255, 255, 255, 0.95);
    justify-content: center;
    align-items: center;
    z-index: 9999;
}

.loading-overlay.active {
    display: flex;
}

.spinner {
    width: 60px;
    height: 60px;
    border: 4px solid #e1e8ed;
    border-top-color: var(--primary-color);
    border-radius: 50%;
    animation: spin 1s linear infinite;
}

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

@media (max-width: 768px) {
    .hero {
        padding: 50px 20px;
    }

    .hero h1 {
        font-size: 2rem;
    }

    .scenario-card {
        padding: 30px 20px;
    }
}