Sample code for implementing a background gradient button using div+css3

<div class="btn_demo">
	<div class="text">Experience</div>
	<div class="arrow">»</div>
</div>

@keyframes arrow_move {
   /* Start state */
    0% {
        left: 130px;
    }
	/* End status */
    100% {
        left: 140px;
    }
}
@keyframes color_move {
    /* Start state */
    0% {
        background-position: 0% 0%; /* horizontal position vertical position */
    }
    50% {
        background-position: 50% 0%;
    }
	/* End status */
    100% {
        background-position: 100% 0%;
    }
}
.btn_demo {
    width:180px;
    height:60px;
    border-radius: 10px;
    position: relative;
    background: linear-gradient( 90deg, #373d42 0%, #2679dd 50%, #373d42 100%);
    background-size: 400% 100%;
    animation: color_move 5s infinite ease-in-out alternate;
    cursor: pointer;
}
.btn_demo:hover {
    background: #2679dd;
}
.btn_demo:active {
    background: #373d42;
}
.btn_demo > .text {
    /* background: yellow; */
    width: 50px;
    text-align: center;
    position: absolute;
    left: 50%;
    top: 50%;
    transform: translate(-50%,-50%);
    font-size: 20px;
    color: #fff;
    font-weight: bold;
}
.btn_demo > .arrow {
    /* background: green; */
    width: 20px;
    text-align: center;
    position: absolute;
    font-size: 30px;
    color: #fff;
    top: 46%;
    transform: translateY(-50%);
    left: 130px; /* move 130~150px */
    /* Call animation */
    animation-name: arrow_move;
    /* Duration */
    animation-duration: 1s;
    /* Infinite playback*/
    animation-iteration-count: infinite;
}