/* IELTS 智能模考系统 - 首页样式 (参照 PET-exam) */
:root {
    --primary: #3b82f6;
    --primary-glow: #60a5fa;
    --accent: #00d2ff;
    --text-light: #f8fafc;
    --text-dim: #94a3b8;
    --glass-bg: rgba(30, 41, 59, 0.7);
    --glass-border: rgba(255, 255, 255, 0.1);
}

@keyframes drift {
    0%, 100% { background-position: 0% 50%; }
    50% { background-position: 100% 50%; }
}

body {
    margin: 0;
    font-family: 'Roboto', 'Noto Sans SC', sans-serif;
    background: linear-gradient(-45deg, #020617, #1e1b4b, #172554, #0f172a);
    background-size: 400% 400%;
    animation: drift 25s ease infinite;
    color: var(--text-light);
    min-height: 100vh;
}

.navbar {
    display: flex; justify-content: space-between; align-items: center;
    padding: 1rem 5%;
    background: rgba(15, 23, 42, 0.6);
    backdrop-filter: blur(12px);
    border-bottom: 1px solid var(--glass-border);
    position: sticky; top: 0; z-index: 100;
}

.btn-logout {
    background: rgba(239, 68, 68, 0.15);
    color: #fca5a5;
    border: 1px solid rgba(239, 68, 68, 0.35);
    padding: 6px 15px;
    border-radius: 20px;
    cursor: pointer;
    font-size: 0.9rem;
    transition: all 0.3s;
    display: flex;
    align-items: center;
    gap: 6px;
}
.btn-logout:hover {
    background: #ef4444;
    color: #fff;
    border-color: #ef4444;
}

.hero {
    text-align: center;
    padding: 5rem 1rem 3rem;
    position: relative;
    overflow: hidden;
}

.hero::before {
    content: ''; position: absolute; top: 50%; left: 50%;
    transform: translate(-50%, -50%);
    width: 60%; height: 200px;
    background: radial-gradient(circle, rgba(59,130,246,0.2) 0%, rgba(0,0,0,0) 70%);
    z-index: -1;
}

.brand-domain {
    font-family: 'Courier New', monospace;
    color: var(--accent);
    font-size: 1rem;
    letter-spacing: 4px;
    text-transform: uppercase;
    margin-bottom: 15px;
    opacity: 0.9;
}

.hero h1 {
    font-size: 3.5rem;
    font-weight: 900;
    margin: 0;
    background: linear-gradient(to bottom, #ffffff 0%, #cbd5e1 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    letter-spacing: -1px;
}

.hero-tagline {
    font-size: 1.2rem;
    margin-top: 15px;
    font-weight: 300;
    letter-spacing: 2px;
    color: var(--text-dim);
}

.main-content {
    max-width: 900px;
    margin: 0 auto;
    padding: 20px;
    display: flex;
    flex-direction: column;
    gap: 20px;
}

.accordion-card {
    background: var(--glass-bg);
    border: 1px solid var(--glass-border);
    border-radius: 16px;
    overflow: hidden;
    backdrop-filter: blur(16px);
    transition: transform 0.3s, box-shadow 0.3s;
    scroll-margin-top: 80px;
}

.accordion-card:hover {
    transform: translateY(-3px);
    box-shadow: 0 10px 25px rgba(0,0,0,0.3);
}

.card-header {
    padding: 20px 30px;
    cursor: pointer;
    display: flex;
    justify-content: space-between;
    align-items: center;
    background: rgba(255,255,255,0.03);
}

.card-header:hover {
    background: rgba(255,255,255,0.08);
}

.header-content {
    display: flex;
    align-items: center;
    gap: 15px;
    font-size: 1.2rem;
    font-weight: 500;
}

.card-icon-small {
    color: var(--accent);
    font-size: 1.4rem;
}

.toggle-icon {
    transition: transform 0.3s;
}

.toggle-icon.rotate {
    transform: rotate(180deg);
}

.accordion-content {
    max-height: 0;
    overflow: hidden;
    transition: max-height 0.4s ease;
    background: rgba(0,0,0,0.3);
}

.accordion-content.active {
    border-top: 1px solid var(--glass-border);
}

.test-grid-container {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(180px, 1fr));
    gap: 15px;
    padding: 25px;
}

.test-unit {
    background: rgba(255,255,255,0.05);
    border-radius: 8px;
    padding: 12px;
    border: 1px solid transparent;
}

.test-unit:hover {
    border-color: var(--primary);
    background: rgba(59, 130, 246, 0.1);
}

.test-title {
    text-align: center;
    color: var(--accent);
    font-weight: bold;
    margin-bottom: 8px;
}

.part-buttons {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 6px;
}

.part-btn {
    text-align: center;
    padding: 8px 4px;
    border-radius: 4px;
    background: rgba(255,255,255,0.1);
    color: #cbd5e1;
    text-decoration: none;
    font-size: 0.8rem;
    transition: all 0.2s;
}

.part-btn:hover {
    background: var(--primary);
    color: white;
}