/* 全局重置和基础样式 */
* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

:root {
    --primary-color: #667eea;
    --primary-dark: #5a6fd8;
    --secondary-color: #764ba2;
    --success-color: #10b981;
    --warning-color: #f59e0b;
    --error-color: #ef4444;
    --text-primary: #1f2937;
    --text-secondary: #6b7280;
    --bg-primary: #ffffff;
    --bg-secondary: #f8fafc;
    --bg-tertiary: #f1f5f9;
    --border-color: #e5e7eb;
    --shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1);
}

html {
    font-size: 16px;
    -webkit-text-size-adjust: 100%;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    line-height: 1.6;
    color: var(--text-primary);
    background: var(--bg-secondary);
    min-height: 100vh;
}

/* 容器布局 */
.container {
    width: 100%;
    max-width: 100%;
    margin: 0 auto;
    padding: 0 16px;
}

@media (min-width: 640px) {
    .container {
        max-width: 640px;
        padding: 0 20px;
    }
}

@media (min-width: 768px) {
    .container {
        max-width: 768px;
        padding: 0 24px;
    }
}

@media (min-width: 1024px) {
    .container {
        max-width: 1024px;
        padding: 0 32px;
    }
}

/* 卡片组件 */
.card {
    background: var(--bg-primary);
    border-radius: 12px;
    box-shadow: var(--shadow);
    padding: 20px;
    margin-bottom: 16px;
    border: 1px solid var(--border-color);
}

.card-lg {
    padding: 24px;
}

/* 按钮样式 */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 12px 20px;
    border: none;
    border-radius: 8px;
    font-size: 16px;
    font-weight: 600;
    text-decoration: none;
    text-align: center;
    cursor: pointer;
    transition: all 0.3s ease;
    min-height: 48px;
    -webkit-tap-highlight-color: transparent;
}

.btn:active {
    transform: scale(0.98);
}

.btn-primary {
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    color: white;
}

.btn-success {
    background: var(--success-color);
    color: white;
}

.btn-warning {
    background: var(--warning-color);
    color: white;
}

.btn-error {
    background: var(--error-color);
    color: white;
}

.btn-outline {
    background: transparent;
    border: 2px solid var(--primary-color);
    color: var(--primary-color);
}

.btn-sm {
    padding: 8px 16px;
    font-size: 14px;
    min-height: 40px;
}

.btn-full {
    width: 100%;
}

/* 表单元素 */
.form-group {
    margin-bottom: 20px;
}

.form-label {
    display: block;
    margin-bottom: 8px;
    font-weight: 600;
    color: var(--text-primary);
}

.form-input {
    width: 100%;
    padding: 14px 16px;
    border: 2px solid var(--border-color);
    border-radius: 8px;
    font-size: 16px;
    transition: border-color 0.3s ease;
    background: var(--bg-primary);
}

.form-input:focus {
    outline: none;
    border-color: var(--primary-color);
}

.form-textarea {
    min-height: 120px;
    resize: vertical;
}

.form-select {
    appearance: none;
    background-image: url("data:image/svg+xml,%3csvg xmlns='http://www.w3.org/2000/svg' fill='none' viewBox='0 0 20 20'%3e%3cpath stroke='%236b7280' stroke-linecap='round' stroke-linejoin='round' stroke-width='1.5' d='m6 8 4 4 4-4'/%3e%3c/svg%3e");
    background-position: right 16px center;
    background-repeat: no-repeat;
    background-size: 16px;
    padding-right: 48px;
}

/* 网格布局 */
.grid {
    display: grid;
    gap: 16px;
}

.grid-1 { grid-template-columns: 1fr; }
.grid-2 { grid-template-columns: 1fr 1fr; }

@media (max-width: 640px) {
    .grid-2 {
        grid-template-columns: 1fr;
    }
}

/* 导航栏 */
.navbar {
    background: var(--bg-primary);
    box-shadow: var(--shadow);
    position: sticky;
    top: 0;
    z-index: 100;
    padding: 16px 0;
}

.nav-content {
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.nav-brand {
    font-size: 20px;
    font-weight: 700;
    color: var(--primary-color);
    text-decoration: none;
}

.nav-menu {
    display: flex;
    gap: 16px;
    align-items: center;
}

.nav-link {
    color: var(--text-primary);
    text-decoration: none;
    padding: 8px 12px;
    border-radius: 6px;
    transition: background-color 0.3s ease;
}

.nav-link:active {
    background: var(--bg-tertiary);
}

/* 移动端菜单 */
.mobile-menu-btn {
    display: none;
    background: none;
    border: none;
    font-size: 24px;
    cursor: pointer;
    padding: 8px;
}

@media (max-width: 768px) {
    .mobile-menu-btn {
        display: block;
    }
    
    .nav-menu {
        display: none;
        position: absolute;
        top: 100%;
        left: 0;
        right: 0;
        background: var(--bg-primary);
        flex-direction: column;
        padding: 16px;
        box-shadow: var(--shadow-lg);
    }
    
    .nav-menu.active {
        display: flex;
    }
}

/* 统计卡片 */
.stats-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
    gap: 16px;
    margin: 24px 0;
}

.stat-card {
    background: var(--bg-primary);
    padding: 20px;
    border-radius: 12px;
    text-align: center;
    box-shadow: var(--shadow);
    border-left: 4px solid var(--primary-color);
}

.stat-number {
    font-size: 28px;
    font-weight: 700;
    color: var(--primary-color);
    margin-bottom: 8px;
}

/* 题目卡片 */
.question-card {
    background: var(--bg-primary);
    border: 2px solid var(--border-color);
    border-radius: 12px;
    padding: 20px;
    margin-bottom: 16px;
    transition: border-color 0.3s ease;
}

.question-card:active {
    border-color: var(--primary-color);
}

.question-text {
    font-size: 18px;
    font-weight: 600;
    margin-bottom: 16px;
    color: var(--text-primary);
}

.options-grid {
    display: grid;
    gap: 12px;
}

.option-item {
    display: flex;
    align-items: flex-start;
    gap: 12px;
    padding: 16px;
    border: 2px solid var(--border-color);
    border-radius: 8px;
    transition: all 0.3s ease;
    cursor: pointer;
}

.option-item:active {
    background: var(--bg-tertiary);
    border-color: var(--primary-color);
}

.option-input {
    margin-top: 2px;
}

.option-label {
    flex: 1;
    font-size: 16px;
}

/* 消息提示 */
.alert {
    padding: 16px;
    border-radius: 8px;
    margin-bottom: 20px;
    border: 1px solid transparent;
}

.alert-success {
    background: #d1fae5;
    border-color: #a7f3d0;
    color: #065f46;
}

.alert-error {
    background: #fee2e2;
    border-color: #fecaca;
    color: #991b1b;
}

.alert-warning {
    background: #fef3c7;
    border-color: #fde68a;
    color: #92400e;
}

/* 工具类 */
.text-center { text-align: center; }
.text-left { text-align: left; }
.text-right { text-align: right; }

.mt-1 { margin-top: 8px; }
.mt-2 { margin-top: 16px; }
.mt-3 { margin-top: 24px; }
.mt-4 { margin-top: 32px; }

.mb-1 { margin-bottom: 8px; }
.mb-2 { margin-bottom: 16px; }
.mb-3 { margin-bottom: 24px; }
.mb-4 { margin-bottom: 32px; }

.p-1 { padding: 8px; }
.p-2 { padding: 16px; }
.p-3 { padding: 24px; }
.p-4 { padding: 32px; }

.hidden { display: none; }
.sr-only { position: absolute; width: 1px; height: 1px; padding: 0; margin: -1px; overflow: hidden; }

/* 防止缩放 */
input, select, textarea, button {
    font-size: 16px;
}

/* 触摸优化 */
@media (hover: none) and (pointer: coarse) {
    .btn, .nav-link, .option-item {
        min-height: 44px;
    }
}