/* ---------- 固定网格背景 ---------- */
:root {
    --cursor-x: 50%;
    --cursor-y: 50%;
    --grid-size: 48px;
    --grid-color: rgba(255, 255, 255, 0.06);
    --grid-glow-color: rgba(120, 180, 255, 0.35);
}

/* 基础网格：永远存在 */
.grid-base {
    position: fixed;
    inset: 0;
    z-index: 0;
    pointer-events: none;
    background-image:
        linear-gradient(var(--grid-color) 1px, transparent 1px),
        linear-gradient(90deg, var(--grid-color) 1px, transparent 1px);
    background-size: var(--grid-size) var(--grid-size);
}

/* 发光网格：只在鼠标附近显示 */
.grid-glow {
    position: fixed;
    inset: 0;
    z-index: 1;
    pointer-events: none;
    background-image:
        linear-gradient(var(--grid-glow-color) 1px, transparent 1px),
        linear-gradient(90deg, var(--grid-glow-color) 1px, transparent 1px);
    background-size: var(--grid-size) var(--grid-size);
    /* 关键：圆形遮罩 */
    -webkit-mask-image: radial-gradient(circle 280px at var(--cursor-x) var(--cursor-y), black 0%, rgba(0, 0, 0, 0.6) 40%, transparent 100%);
    mask-image: radial-gradient(circle 280px at var(--cursor-x) var(--cursor-y), black 0%, rgba(0, 0, 0, 0.6) 40%, transparent 100%);
    mix-blend-mode: screen;
    opacity: 0.9;
}

/* 响应式：背景 */
@media (max-width: 768px) {
    .grid-glow {
        opacity: 0.5;
    }
}

@media (max-width: 480px) {
    .grid-glow {
        display: none;
    }
}