<button class="button--wipe">Wipe left to right</button>

<button class="button--wipe button--wipe-vertical">Wipe top to bottom</button>

/**
 * Button wipe with NO pseudo-elements
 */


/* button--wipe */

.button--wipe {
    --bg-color: thistle;
    --bg-color-hover: darkorange;
    --bg-size: 0% 100%;
    --duration: 300ms;
    --easing: cubic-bezier(0.165, 0.840, 0.440, 1);
    --padding-x: 1.5rem;
    --padding-y: 1rem;
    --wipe-dir: 90deg;
        
    background-color: var(--bg-color);
    background-image: linear-gradient(var(--wipe-dir), var(--bg-color-hover), var(--bg-color-hover));
    background-repeat: no-repeat;
    background-size: var(--bg-size);
    color: black;
    display: inline-block;
    padding: var(--padding-y) var(--padding-x);
    transition: background-size var(--duration) var(--easing);
}

.button--wipe:hover {
    --bg-size: 100% 100%;
    
    background-image: linear-gradient(var(--wipe-dir), var(--bg-color-hover), var(--bg-color-hover));
    background-size: var(--bg-size);
}


/* button--wipe-vertical */

.button--wipe-vertical {
    --bg-size: 100% 0%;
    --wipe-dir: 180deg;
}


/**
 * demo styles
 */

* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

body {
    background-color: ghostwhite;
    font-family: system-ui, -apple-system, sans-serif;
    padding: 1rem;
}

button {
    border: 0;
    cursor: pointer;
    font-family: system-ui, -apple-system, sans-serif;
    font-weight: 600;
}