styles.css

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}
.page {
    display: flex;
    flex-wrap: wrap;
}
.section {
    width: 100%;
    height: 300px;
    display: flex;
    justify-content: center;
    align-items: center;
}
.menu {
    background-color: #5995DA;
    height: 80px;
}
.header {
    background-color: #B2D6FF;
}
.content {
    background-color: #EAEDF0;
    height: 600px;
}
.sign-up {
    background-color: #D6E9FE;
}
.feature-1 {
    background-color: #F5CF8E;
}
.feature-2 {
    background-color: #F09A9D;
}
.feature-3 {
    background-color: #C8C6FA;
}
.illustration img {
    width: 100%;
    display: block;
}
.header {
    height: auto;
    justify-content: inherit;
    align-items: inherit;
  }
.photo img {
    width: 100%;
    display: block;
}
/* Mobile Styles */
@media only screen and (max-width: 400px) {
    body {
        background-color: #F09A9D;
       /* Red */
   }
}
/* Tablet Styles */
@media only screen and (min-width: 401px) and (max-width: 960px) {
    .sign-up, .feature-1, .feature-2, .feature-3 {
        width: 50%;
   }
}
/* Desktop Styles */
@media only screen and (min-width: 961px) {
    .page {
        width: 960px;
        margin: 0 auto;
   }
    .feature-1, .feature-2, .feature-3 {
        width: 33.3%;
   }
    .header {
        height: 400px;
   }
    .sign-up {
        height: 200px;
        order: 1;
   }
    .content {
        order: 2;
   }
}