/**
 * 胶片颗粒全局质感叠加层
 * 模拟老照片的颗粒感，增加复古氛围
 */

.film-grain-overlay {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    pointer-events: none;
    z-index: 9999;
    opacity: 0.04;
    animation: grain 0.5s steps(1) infinite;
}

/* 使用伪元素直接生成噪点，避免加载外部图片 */
.film-grain-overlay::before {
    content: '';
    position: absolute;
    top: -50%;
    left: -50%;
    width: 200%;
    height: 200%;
    background-image: url("data:image/svg+xml,%3Csvg viewBox='0 0 256 256' xmlns='http://www.w3.org/2000/svg'%3E%3Cfilter id='noise'%3E%3CfeTurbulence type='fractalNoise' baseFrequency='0.9' numOctaves='4' stitchTiles='stitch'/%3E%3C/filter%3E%3Crect width='100%25' height='100%25' filter='url(%23noise)'/%3E%3C/svg%3E");
    background-repeat: repeat;
}

@keyframes grain {
    0%, 100% { transform: translate(0, 0); }
    10% { transform: translate(-1%, -1%); }
    20% { transform: translate(1%, 1%); }
    30% { transform: translate(-1%, 1%); }
    40% { transform: translate(1%, -1%); }
    50% { transform: translate(-1%, 0%); }
    60% { transform: translate(1%, 0%); }
    70% { transform: translate(0%, 1%); }
    80% { transform: translate(0%, -1%); }
    90% { transform: translate(1%, 1%); }
}

/* 移动端降低颗粒密度 */
@media (max-width: 768px) {
    .film-grain-overlay {
        opacity: 0.025;
    }
}

/* 弱motion用户关闭动画 */
@media (prefers-reduced-motion: reduce) {
    .film-grain-overlay {
        animation: none;
    }
}