@supports not (--css: variables) {
    /* 为不支持CSS变量的浏览器提供回退值 */
    body {
        color: #333;
        background-color: #fff;
    }
    
    .header {
        background: #2c3e50;
        box-shadow: 0 2px 10px rgba(0,0,0,0.1);
    }
    
    .nav a {
        border-radius: 8px;
        transition: all 0.3s ease;
    }
    
    .banner {
        background: linear-gradient(135deg, #3498db, #2c3e50);
        border-radius: 8px;
    }
    
    .software-item {
        border-radius: 8px;
        box-shadow: 0 4px 15px rgba(0,0,0,0.08);
        transition: all 0.3s ease;
    }
    
    .section-title {
        color: #2c3e50;
        border-left: 4px solid #3498db;
    }
}

/* IE11特定修复 */
@media all and (-ms-high-contrast: none), (-ms-high-contrast: active) {
    /* IE11不支持CSS Grid，使用flexbox回退 */
    .software-grid {
        display: -ms-flexbox;
        display: flex;
        -ms-flex-wrap: wrap;
        flex-wrap: wrap;
        margin: -1rem;
    }
    
    .software-item {
        -ms-flex: 0 0 calc(33.333% - 2rem);
        flex: 0 0 calc(33.333% - 2rem);
        margin: 1rem;
    }
    
    /* IE11不支持object-fit */
    .software-image img {
        width: auto;
        height: auto;
        max-width: 100%;
        max-height: 200px;
        margin: 0 auto;
        display: block;
    }
    
    /* IE11不支持sticky定位 */
    .header {
        position: fixed;
        width: 100%;
    }
    
    .main {
        padding-top: 80px; /* 为固定头部留出空间 */
    }
}

/* Safari特定修复 */
_::-webkit-full-page-media, _:future, :root .safari_only {
    /* Safari的flexbox和grid修复 */
    .software-grid {
        display: -webkit-flex;
        display: flex;
        -webkit-flex-wrap: wrap;
        flex-wrap: wrap;
    }
    
    /* Safari的transform修复 */
    .software-item:hover {
        -webkit-transform: translateY(-3px);
        transform: translateY(-3px);
    }
}

/* Firefox特定修复 */
@-moz-document url-prefix() {
    /* Firefox的滚动条样式修复 */
    * {
        scrollbar-width: thin;
        scrollbar-color: #3498db #f0f0f0;
    }
    
    /* Firefox的渐变修复 */
    .banner {
        background: -moz-linear-gradient(135deg, #3498db, #2c3e50);
    }
}

/* 移动端浏览器修复 */
@media (max-width: 768px) {
    /* 移动端touch-action优化 */
    .nav a, .download-btn, .search-box button {
        -webkit-tap-highlight-color: transparent;
        touch-action: manipulation;
    }
    
    /* 移动端滚动优化 */
    html {
        -webkit-overflow-scrolling: touch;
    }
}

/* 旧版Android浏览器修复 */
@media screen and (-webkit-min-device-pixel-ratio:0) and (min-resolution:.001dpcm) {
    /* Android 4.x浏览器修复 */
    .software-grid {
        display: -webkit-box;
        display: -webkit-flex;
        display: flex;
        -webkit-flex-wrap: wrap;
        flex-wrap: wrap;
    }
    
    .software-item {
        -webkit-box-flex: 1;
        -webkit-flex: 1;
        flex: 1;
        min-width: 300px;
        margin: 10px;
    }
}

/* 高DPI屏幕优化 */
@media (-webkit-min-device-pixel-ratio: 2), (min-resolution: 192dpi) {
    /* 高DPI屏幕下的边框和阴影优化 */
    .software-item {
        border-width: 0.5px;
    }
    
    .header {
        box-shadow: 0 1px 5px rgba(0,0,0,0.1);
    }
}

/* 打印样式优化 */
@media print {
    .header, .footer, .banner {
        display: none;
    }
    
    .software-item {
        box-shadow: none;
        border: 1px solid #ccc;
        break-inside: avoid;
    }
    
    .software-image img {
        filter: grayscale(100%);
    }
}