<div class="wrapper">
<div class="aside"></div>
<div class="main"></div>
<div class="form"></div>
</div>
<style>
.wrapper {
display: flex;
flex-direction: row;
}
@media(min-width: 320px) and (max-width: 990px) {
.wrapper {
display: flex;
flex-direction: column;
}
}
</style>