<style>
.ボタン{position:absolute;
top:100px;
left:100px;
background-color:black;
color:white;
padding:10px 20px;
border:none;
border-radius:6px;
font-size:16px;
cursor:pointer;
animation:バウンス 1s infinite;}
@keyframes バウンス{0%,100%{transform:translateY(0);}
50%{transform:translateY(-10px);}}
</style>

<button class="ボタン">バウンス</button>