<!DOCTYPE html>
<html>
<head>
<style>
body {
width: 300px;
height: 300px;
overflow: hidden;
margin: 0;
padding: 0;
}
button {
display: block;
margin: 0;
padding: 0;
border: 0;
width: 100px;
height: 50px;
position: absolute;
}
#b1 {
left: 0;
top: 0;
background-color: #090;
}
#b2 {
left: 0;
top: 150px;
background-color: #900;
}
</style>
</head>
<body><button id="b1" aria-label="Button 1"></button><button id="b2" aria-label="Button 2"></button></body>