/* 全局样式 */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'Arial', sans-serif;
}

/* 颜色定义 - 天空蓝 & 素描黑 */
:root {
    --sky-blue: #87CEEB;
    --sky-blue-dark: #4FC3F7;
    --sketch-black: #2C2C2C;
    --light-gray: #f5f5f5;
    --white: #ffffff;
    --shadow: 0 4px 8px rgba(0, 0, 0, 0.1);
}

body {
    background-color: var(--light-gray);
    color: var(--sketch-black);
    line-height: 1.6;
}

/* 头部样式 */
header {
    background-color: var(--white);
    padding: 1rem 5%;
    box-shadow: var(--shadow);
    display: flex;
    justify-content: space-between;
    align-items: center;
    position: sticky;
    top: 0;
    z-index: 100;
}

.logo {
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.logo img {
    height: 40px;
}

.logo h1 {
    color: var(--sky-blue-dark);
    font-size: 1.5rem;
}

nav ul {
    display: flex;
    list-style: none;
    gap: 2rem;
}

nav a {
    color: var(--sketch-black);
    text-decoration: none;
    font-weight: 500;
    transition: color 0.3s;
}

nav a:hover {
    color: var(--sky-blue-dark);
}

/* 田字形布局容器 */
.grid-container {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 2rem;
    padding: 2rem 5%;
    max-width: 1400px;
    margin: 0 auto;
}

/* 网格项样式 */
.grid-item {
    background-color: var(--white);
    padding: 2rem;
    border-radius: 10px;
    box-shadow: var(--shadow);
    transition: transform 0.3s;
}

.grid-item:hover {
    transform: translateY(-5px);
}

/* 浮动产品图片 */
.floating-img {
    position: relative;
    animation: float 3s ease-in-out infinite;
    max-width: 100%;
    border-radius: 8px;
}

@keyframes float {
    0% { transform: translateY(0px); }
    50% { transform: translateY(-10px); }
    100% { transform: translateY(0px); }
}

/* 产品介绍样式 */
.product-intro {
    grid-column: 1 / -1; /* 跨两列 */
    background: linear-gradient(135deg, var(--sky-blue), var(--sky-blue-dark));
    color: var(--white);
    text-align: center;
}

.product-intro h2 {
    font-size: 2rem;
    margin-bottom: 1rem;
}

/* 文章样式 */
.article-card {
    margin-bottom: 1.5rem;
}

.article-card h3 {
    color: var(--sky-blue-dark);
    margin-bottom: 0.5rem;
}

.article-card p {
    color: var(--sketch-black);
    margin-bottom: 1rem;
}

.article-card a {
    color: var(--sky-blue-dark);
    text-decoration: none;
    font-weight: 500;
}

/* 下载按钮样式 */
.download-btn {
    display: inline-block;
    background-color: var(--sky-blue-dark);
    color: var(--white);
    padding: 0.8rem 2rem;
    border-radius: 50px;
    text-decoration: none;
    font-weight: 600;
    transition: background-color 0.3s;
    margin-top: 1rem;
}

.download-btn:hover {
    background-color: #2196F3;
}

/* 页脚样式 */
footer {
    background-color: var(--sketch-black);
    color: var(--white);
    text-align: center;
    padding: 2rem 5%;
    margin-top: 2rem;
}

/* 404页面样式 */
.error-page {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    height: 80vh;
    text-align: center;
    padding: 2rem;
}

.error-page h2 {
    font-size: 8rem;
    color: var(--sky-blue-dark);
    margin-bottom: 1rem;
}

.error-page h3 {
    font-size: 2rem;
    margin-bottom: 1rem;
}

.error-page p {
    margin-bottom: 2rem;
    max-width: 600px;
}

/* 响应式适配 */
@media (max-width: 768px) {
    .grid-container {
        grid-template-columns: 1fr;
    }
    
    nav ul {
        gap: 1rem;
    }
}