.glow-on-hover {
    width: 280px;
    height: 50px;
    border: none;
    outline: none;
    color: #fff;
    background: #111;
    cursor: pointer;
    position: relative;
    z-index: 0;
    border-radius: 10px;
}

.glow-on-hover:before {
    content: '';
    background: linear-gradient(45deg, #ff0000, #ff7300, #fffb00, #48ff00, #00ffd5, #002bff, #7a00ff, #ff00c8, #ff0000);
    position: absolute;
    top: -2px;
    left:-2px;
    background-size: 400%;
    z-index: -1;
    filter: blur(5px);
    width: calc(100% + 4px);
    height: calc(100% + 4px);
    animation: glowing 20s linear infinite;
    opacity: 0;
    transition: opacity .3s ease-in-out;
    border-radius: 10px;
}


.glow-on-hover:active {
    color: #000
}

.glow-on-hover:active:after {
    background: transparent;
}


.glow-on-hover:hover:before {
    opacity: 1;
}

.glow-on-hover:after {
    z-index: -1;
    content: '';
    position: absolute;
    width: 100%;
    height: 100%;
    background: #111;
    left: 0;
    top: 0;
    border-radius: 10px;
}


@keyframes glowing {
    0% { background-position: 0 0; }
    50% { background-position: 400% 0; }
    100% { background-position: 0 0; }
}

.glow.play,
.glow.pause {
    width: auto;
    min-width: 350px;
    max-width: 350px;
    height: 50px;
    border: none;
    outline: none;
    color: #fff;
    background: #111;
    cursor: pointer;
    position: relative;
    z-index: 0;
    border-radius: 10px;
    text-transform: capitalize;
}

.glow.play:before {
    content: '';
    background: linear-gradient(45deg, #ff0000, #ff7300, #fffb00, #48ff00, #00ffd5, #002bff, #7a00ff, #ff00c8, #ff0000);
    position: absolute;
    top: -2px;
    left:-2px;
    background-size: 400%;
    z-index: -1;
    filter: blur(5px);
    width: calc(100% + 4px);
    height: calc(100% + 4px);
    animation: glowing 20s linear infinite;
    opacity: 1;
    transition: opacity .3s ease-in-out;
    border-radius: 10px;
}

.glow.pause:before {
    content: '';
    background: linear-gradient(45deg, #ff0000, #ff7300, #fffb00, #48ff00, #00ffd5, #002bff, #7a00ff, #ff00c8, #ff0000);
    position: absolute;
    top: -2px;
    left:-2px;
    background-size: 400%;
    z-index: -1;
    filter: blur(5px);
    width: calc(100% + 4px);
    height: calc(100% + 4px);
    animation: glowing 20s linear infinite;
    opacity: 0;
    transition: opacity .3s ease-in-out;
    border-radius: 10px;
}

.glow.pause:after,
.glow.play:after {
    z-index: -1;
    content: '';
    position: absolute;
    width: var(--progress, 100%); /* JS управляет шириной */
    height: 100%;
    background: #111;
    left: 0;
    top: 0;
    border-radius: 10px;
}

.glow.play:active:after,
.glow.pause:active:after {
    background: transparent;
}

.glow.pause:active,
.glow.play:active {
    color: #000
}

.glowsmall.play,
.glowsmall.pause {
    width: auto;
    min-width: 90px;
    max-width: 90px;
    height: 50px;
    border: none;
    outline: none;
    color: #fff;
    background: #111;
    cursor: pointer;
    position: relative;
    z-index: 0;
    border-radius: 10px;
    text-transform: capitalize;
    padding: 0;
}

.glowsmall.play:before {
    content: '';
    background: linear-gradient(45deg, #ff0000, #ff7300, #fffb00, #48ff00, #00ffd5, #002bff, #7a00ff, #ff00c8, #ff0000);
    position: absolute;
    top: -2px;
    left:-2px;
    background-size: 400%;
    z-index: -1;
    filter: blur(5px);
    width: calc(100% + 4px);
    height: calc(100% + 4px);
    animation: glowing 20s linear infinite;
    opacity: 1;
    transition: opacity .3s ease-in-out;
    border-radius: 10px;
}

.glowsmall.pause:before {
    content: '';
    background: linear-gradient(45deg, #ff0000, #ff7300, #fffb00, #48ff00, #00ffd5, #002bff, #7a00ff, #ff00c8, #ff0000);
    position: absolute;
    top: -2px;
    left:-2px;
    background-size: 400%;
    z-index: -1;
    filter: blur(5px);
    width: calc(100% + 4px);
    height: calc(100% + 4px);
    animation: glowing 20s linear infinite;
    opacity: 0;
    transition: opacity .3s ease-in-out;
    border-radius: 10px;
}

.glowsmall.pause:after,
.glowsmall.play:after {
    z-index: -1;
    content: '';
    position: absolute;
    width: 100%;
    height: 100%;
    background: #111;
    left: 0;
    top: 0;
    border-radius: 10px;
}

.glowsmall.play:active:after,
.glowsmall.pause:active:after {
    background: transparent;
}

.glowsmall.pause:active,
.glowsmall.play:active {
    color: #000
}