/* --- 背景与光效 --- */
.background {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    z-index: -1;
    overflow: hidden;
}

.ambient-glow {
    position: absolute;
    border-radius: 50%;
    filter: blur(120px);
    opacity: 0.5;
    animation: breathe 8s infinite alternate ease-in-out;
}

.glow-1 {
    width: 600px;
    height: 600px;
    background: radial-gradient(circle, var(--primary-color), transparent 70%);
    top: -10%;
    left: -10%;
}

.glow-2 {
    width: 500px;
    height: 500px;
    background: radial-gradient(circle, var(--secondary-color), transparent 70%);
    bottom: -10%;
    right: -10%;
    animation-delay: -4s;
}

.grid-overlay {
    position: absolute;
    width: 200%;
    height: 200%;
    top: -50%;
    left: -50%;
    background-image:
        linear-gradient(rgba(255, 255, 255, 0.03) 1px, transparent 1px),
        linear-gradient(90deg, rgba(255, 255, 255, 0.03) 1px, transparent 1px);
    background-size: 40px 40px;
    transform: perspective(500px) rotateX(60deg) translateY(-100px) translateZ(-200px);
    animation: grid-move 20s linear infinite;
    opacity: 0.3;
}

#particles {
    position: absolute;
    width: 100%;
    height: 100%;
}

.particle {
    position: absolute;
    background: white;
    border-radius: 50%;
    animation: float-up linear infinite;
}

@keyframes breathe {
    0% {
        transform: scale(1);
        opacity: 0.3;
    }

    100% {
        transform: scale(1.2);
        opacity: 0.6;
    }
}

@keyframes grid-move {
    0% {
        transform: perspective(500px) rotateX(60deg) translateY(0) translateZ(-200px);
    }

    100% {
        transform: perspective(500px) rotateX(60deg) translateY(40px) translateZ(-200px);
    }
}

@keyframes float-up {
    100% {
        transform: translateY(-100vh);
        opacity: 0;
    }
}