:root {
    /* 主题颜色 */
    --primary-color: #4a90e2;
    --secondary-color: #6c757d;
    --success-color: #28a745;
    --danger-color: #dc3545;
    --warning-color: #ffc107;
    --info-color: #17a2b8;
    
    /* 文本颜色 */
    --text-primary: #2c3e50;
    --text-secondary: #6c757d;
    --text-muted: #95a5a6;
    
    /* 背景颜色 */
    --bg-primary: #ffffff;
    --bg-secondary: #f8f9fa;
    --card-bg: #ffffff;
    --input-bg: #ffffff;
    
    /* 边框颜色 */
    --border-color: #e9ecef;
    
    /* 阴影 */
    --shadow-sm: 0 1px 3px rgba(0,0,0,0.12);
    --shadow-md: 0 4px 6px rgba(0,0,0,0.1);
    --shadow-lg: 0 10px 15px rgba(0,0,0,0.1);
    
    /* 圆角 */
    --border-radius-sm: 4px;
    --border-radius-md: 8px;
    --border-radius-lg: 12px;
}

/* 基础样式 */
body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
    color: var(--text-primary);
    background-color: var(--bg-secondary);
    line-height: 1.5;
    margin: 0;
    padding: 0;
}

/* 容器 */
.container {
    width: 100%;
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 1rem;
}

/* 按钮样式 */
.btn {
    display: inline-block;
    font-weight: 500;
    text-align: center;
    white-space: nowrap;
    vertical-align: middle;
    user-select: none;
    border: 1px solid transparent;
    padding: 0.5rem 1rem;
    font-size: 1rem;
    line-height: 1.5;
    border-radius: var(--border-radius-md);
    transition: all 0.3s ease;
    cursor: pointer;
}

.btn-primary {
    color: #fff;
    background-color: var(--primary-color);
    border-color: var(--primary-color);
}

.btn-primary:hover {
    background-color: #357abd;
    border-color: #357abd;
}

/* 表单样式 */
.form-control {
    display: block;
    width: 100%;
    padding: 0.5rem 0.75rem;
    font-size: 1rem;
    line-height: 1.5;
    color: var(--text-primary);
    background-color: var(--input-bg);
    background-clip: padding-box;
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius-md);
    transition: border-color 0.15s ease-in-out, box-shadow 0.15s ease-in-out;
}

.form-control:focus {
    color: var(--text-primary);
    background-color: var(--input-bg);
    border-color: var(--primary-color);
    outline: 0;
    box-shadow: 0 0 0 0.2rem rgba(74, 144, 226, 0.25);
}

/* 卡片样式 */
.card {
    position: relative;
    display: flex;
    flex-direction: column;
    min-width: 0;
    word-wrap: break-word;
    background-color: var(--card-bg);
    background-clip: border-box;
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius-lg);
    box-shadow: var(--shadow-md);
}

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

.mt-1 { margin-top: 0.25rem; }
.mt-2 { margin-top: 0.5rem; }
.mt-3 { margin-top: 1rem; }
.mt-4 { margin-top: 1.5rem; }
.mt-5 { margin-top: 3rem; }

.mb-1 { margin-bottom: 0.25rem; }
.mb-2 { margin-bottom: 0.5rem; }
.mb-3 { margin-bottom: 1rem; }
.mb-4 { margin-bottom: 1.5rem; }
.mb-5 { margin-bottom: 3rem; }

/* 响应式设计 */
@media (max-width: 768px) {
    .container {
        padding: 0 0.5rem;
    }
}

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

.fade-in {
    animation: fadeIn 0.3s ease-in;
}

/* 加载动画 */
.spinner-border {
    display: inline-block;
    width: 1rem;
    height: 1rem;
    vertical-align: text-bottom;
    border: 0.2em solid currentColor;
    border-right-color: transparent;
    border-radius: 50%;
    animation: spinner-border 0.75s linear infinite;
}

@keyframes spinner-border {
    to { transform: rotate(360deg); }
}