HTML CSS - Responsive buttons (grid)

Question

I have this portion in a website wherein there are buttons that looks like a grid, but they are just aligned by the usual css. It also only has 1 div which serves as its container. Is it possible to make the buttons responsive so that when the window is scaled larger or smaller, the buttons will still be in place? Thanks!

HTML

    <div class="middle">
        <center>
        <br>
        <br>
        <button type="button3" class="button3">
        <a href="301.html">301</a>
        </button> 
        <button type="button3" class="button3">
        <a href="305.html">305</a>
        </button>
        <button type="button3" class="button3">
        <a href="308.html">308</a>
        </button>
        <br>

        <button type="button3" class="button3">
        <a href="303.html">303</a>
        </button> 
        <button type="button3" class="button3">
        <a href="306.html">306</a>
        </button> 
        <button type="button3" class="button3">
        <a href="309.html">309</a>
        </button> 
        <br>

        <button type="button3" class="button3">
        <a href="304.html">304</a>
        </button>
        <button type="button3" class="button3">
        <a href="307.html">307</a>
        </button>
        <button type="button3" class="button3">
        <a href="310.html">310</a>
        </button> 
        <br>

        <button type="button3" class="button3">
        <a href="311.html">311</a>
        </button> 
        <button type="button3" class="button3">
        <a href="312.html">312</a>
        </button>



        </center>
    </div>  

CSS

.button {
height: 40px;
width: 130px;
margin-bottom: 3%;
background-color: #7C8082;
font-size: 100%;
color: white;
font-family: 'Muli', sans-serif;
border-radius: 5px;
border-color: #ffffff;
}

    .button:hover {
background-color: #474240;
    font-family: 'Muli', sans-serif;
}   

    .button1 {
height: 40px;
width: 70px;
background-color: #7C8082;
font-size: 100%;
color: white;
    font-family: 'Muli', sans-serif;
border-radius: 5px;
margin-top:5px;
}
     .button1:hover {
background-color: #474240;
}

    .button3 {
height: 40px;
width: 70px;
background-color: #7C8082;
font-size: 100%;
color: white;
     font-family: 'Muli', sans-serif;
border-radius: 5px;
margin-top:10px;
}

    .button3:hover {
background-color: #474240;
    }

Answer 1

Just update width in percentage for .button3 class as below

.button3 {
   width: 30%;
}

Demo