How to make buttons responsive?

I want to make these buttons responsive in css. I tried setting the width to a percentage value but they just overlap each other at lower resolutions.
Website: chirecmun.org
Here is the code for them:

.enter-container {
    position: relative;
    display: table-cell;
    text-align: center;
    vertical-align: middle;
width:10%;
}

.enter-button, .enter-button2 {
    border: 3px solid #2EA3F2;
    color: #2EA3F2;
    outline: none;
    font-family: inherit;
    font-size: inherit;
    background: none;
    cursor: pointer;
    padding: 2em 6em;
    display: inline-block;
    text-transform: uppercase;
    letter-spacing: 1px;
    font-weight: 700;
    outline: none;
    -webkit-transition: all 0.3s;
    -moz-transition: all 0.3s;
    transition: all 0.3s;
    z-index: 101;
   top: 65%;
   position: absolute;
width:10%;

}
 .enter-button {
left:25%;

}
.enter-button2{
right:25%;

}
.enter-button:hover {
    background-color: #008CBA;
    color: white;
}
.enter-button2:hover {
    background-color: #008CBA;
    color: white;
}