/* animate a CSS variable through rainbow stops */
@keyframes rainbow-colors {
    0%   { --c: #ff004d; }  /* red/pink */
    14%  { --c: #ff7f00; }  /* orange */
    28%  { --c: #fff200; }  /* yellow */
    42%  { --c: #00ff6a; }  /* green */
    57%  { --c: #00b3ff; }  /* cyan/blue */
    71%  { --c: #4b00ff; }  /* indigo */
    85%  { --c: #d100ff; }  /* violet */
    100% { --c: #ff004d; }  /* loop back */
}

.rainbow-flash {
    text-align: center;
    background-color: #000;

    font-family: "Helvetica Neue", Arial, sans-serif;
    font-size: 3rem;
    font-weight:900;
    --c: #ff0000;
    color: var(--c);
    /* layered glow for depth */
    text-shadow:
        0 0 6px rgba(255,255,255,0.15),
        0 0 14px var(--c),
        0 0 28px var(--c),
        0 0 48px rgba(0,0,0,0.35);
    animation: rainbow-colors 4s linear infinite;
}

.main-page-wrapper {
    display: flex;
    justify-content: center;
    align-items: center;
}

.play-button {
    margin-top: 20px;
    width: 150px;
    height: 50px;
    font-size: 18px;
    font-weight: bold;
    text-transform: uppercase;
    color: #fff;
    border: none;
    border-radius: 5px;
    cursor: pointer;
}