.crt {
    position: fixed;   /* lock to screen */
    top: 0; 
    left: 0;
    width: 100%;
    height: 100%;
    pointer-events: none; /* let clicks pass through */
    z-index: 9999;
}

/* Scanlines + flicker */
.crt::before {
    content: "";
    position: absolute;
    top: 0; left: 0;
    width: 100%; height: 100%;
    background: repeating-linear-gradient(
        to bottom,
        rgba(255, 255, 255, 0.02) 0px,
        rgba(255, 255, 255, 0.01) 1px,
        transparent 2px
    );
    animation: flicker 0.15s infinite;
}

.crt::after {
    content: "";
    position: absolute;
    top: 0; left: 0;
    width: 100%; height: 100%;
    background: rgba(0, 0, 0, 0.267);
    mix-blend-mode: multiply;
    pointer-events: none;
}

@keyframes flicker {
    0%, 19%, 21%, 23%, 25%, 54%, 56%, 100% { opacity: 1; }
    20%, 22%, 24%, 55% { opacity: .1; }
}