:root {
    --primary-color: #2563eb;
    --bg-color: #f8fafc;
    --panel-bg: #ffffff;
    --border-color: #e2e8f0;
    --text-main: #1e293b;
    --text-muted: #64748b;
}

body, html {
    margin: 0;
    padding: 0;
    height: 100%;
    font-family: 'Inter', -apple-system, sans-serif;
    background-color: var(--bg-color);
    color: var(--text-main);
    overflow: hidden;
}

.layout-container {
    display: flex;
    height: 100vh;
    width: 100vw;
}

/* 左侧作业区 */
.left-panel {
    flex: 0 0 450px;
    background: var(--panel-bg);
    border-right: 1px solid var(--border-color);
    display: flex;
    flex-direction: column;
    box-shadow: 4px 0 15px rgba(0,0,0,0.02);
    z-index: 10;
}

.header {
    padding: 20px;
    border-bottom: 1px solid var(--border-color);
    background: #fff;
}

.header h1 {
    font-size: 1.25rem;
    margin: 0;
    color: var(--primary-color);
}

.content-area {
    padding: 24px;
    flex-grow: 1;
    overflow-y: auto;
}

.card {
    background: #fff;
    border: 1px solid var(--border-color);
    border-radius: 12px;
    padding: 16px;
    margin-bottom: 20px;
}

.card-title {
    font-weight: 600;
    margin-bottom: 12px;
    display: flex;
    align-items: center;
    gap: 8px;
}

.input-group {
    margin-bottom: 16px;
}

.input-group label {
    display: block;
    font-size: 0.875rem;
    color: var(--text-muted);
    margin-bottom: 4px;
}

.input-group input, .input-group select {
    width: 100%;
    padding: 10px;
    border: 1px solid var(--border-color);
    border-radius: 6px;
    font-size: 1rem;
}

.btn {
    background: var(--primary-color);
    color: white;
    border: none;
    padding: 12px 24px;
    border-radius: 8px;
    font-weight: 600;
    cursor: pointer;
    width: 100%;
    transition: background 0.2s;
}

.btn:hover {
    background: #1d4ed8;
}

/* 右侧 PDF 预览区 */
.right-panel {
    flex-grow: 1;
    background: #525659; /* PDF Viewer 常用背景色 */
    position: relative;
    display: flex;
    justify-content: center;
    align-items: center;
}

.pdf-placeholder {
    width: 100%;
    height: 100%;
    border: none;
    background: white;
}

/* 登录页样式 */
.login-container {
    height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    background: linear-gradient(135deg, #2563eb 0%, #1d4ed8 100%);
}

.login-card {
    background: white;
    padding: 40px;
    border-radius: 16px;
    box-shadow: 0 10px 25px rgba(0,0,0,0.1);
    width: 100%;
    max-width: 400px;
}

.login-card h2 {
    margin-top: 0;
    text-align: center;
    color: var(--text-main);
    margin-bottom: 30px;
}

/* 首页样式 */
.hero-section {
    padding: 80px 20px;
    text-align: center;
    background: white;
    border-bottom: 1px solid var(--border-color);
}

.hero-section h1 {
    font-size: 3rem;
    color: var(--primary-color);
    margin-bottom: 16px;
}

.hero-section p {
    font-size: 1.25rem;
    color: var(--text-muted);
    max-width: 600px;
    margin: 0 auto 32px;
}

.features-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 24px;
    padding: 40px 20px;
    max-width: 1200px;
    margin: 0 auto;
}

.feature-card {
    background: white;
    padding: 32px;
    border-radius: 12px;
    border: 1px solid var(--border-color);
    transition: transform 0.2s, box-shadow 0.2s;
    text-decoration: none;
    color: inherit;
}

.feature-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 10px 20px rgba(0,0,0,0.05);
}

/* 统计卡片 */
.stats-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 20px;
    margin-bottom: 30px;
}

.stat-card {
    background: white;
    padding: 24px;
    border-radius: 12px;
    border: 1px solid var(--border-color);
}

.stat-value {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--primary-color);
}

.stat-label {
    font-size: 0.875rem;
    color: var(--text-muted);
}

/* 数据表格 */
.table-container {
    background: white;
    border-radius: 12px;
    border: 1px solid var(--border-color);
    overflow: hidden;
}

table {
    width: 100%;
    border-collapse: collapse;
    text-align: left;
}

th {
    background: #f8fafc;
    padding: 16px;
    font-size: 0.875rem;
    color: var(--text-muted);
    font-weight: 600;
    border-bottom: 1px solid var(--border-color);
}

td {
    padding: 16px;
    border-bottom: 1px solid var(--border-color);
    font-size: 0.935rem;
}

.badge {
    padding: 4px 10px;
    border-radius: 99px;
    font-size: 0.75rem;
    font-weight: 600;
}

.badge-pending { background: #fff7ed; color: #9a3412; }
.badge-processing { background: #eff6ff; color: #1e40af; }
.badge-completed { background: #f0fdf4; color: #166534; }