style.css

@import url("https://fonts.googleapis.com/css2?family=Roboto&display=swap");

:root {
  --left-bg-color: rgba(87, 84, 236, 0.7);
  --right-bg-color: rgba(43, 43, 43, 0.8);
  --left-btn-hover-color: rgba(87, 84, 236, 1);
  --right-btn-hover-color: rgba(28, 122, 28, 1);
  --hover-width: 80%;
  --other-width: 20%;
  --speed: 1s;
}

* {
  box-sizing: border-box;
}

body {
  font-family: "Roboto", sans-serif;
  height: 100vh;
  overflow: hidden;
  margin: 0;
}

h1 {
  font-size: 4rem;
  color: #fff;
  position: absolute;
  left: 50%;
  top: 20%;
  transform: translateX(-50%);
  white-space: nowrap;
}

.btn {
  position: absolute;
  display: flex;
  align-items: center;
  justify-content: center;
  left: 50%;
  top: 40%;
  transform: translateX(-50%);
  text-decoration: none;
  color: #fff;
  border: #fff solid 0.2rem;
  font-size: 1rem;
  font-weight: bold;
  text-transform: uppercase;
  width: 15rem;
  padding: 1.5rem;
}

.split.left .btn:hover {
  background-color: var(--left-btn-hover-color);
  border-color: var(--left-btn-hover-color);
}
.split.right .btn:hover {
  background-color: var(--right-btn-hover-color);
  border-color: var(--right-btn-hover-color);
}

.container {
  position: relative;
  width: 100%;
  height: 100%;
  background-color: #333;
}

.split {
  position: absolute;
  width: 50%;
  height: 100%;
  overflow: hidden;
  transition: var(--speed) ease;
}

.split.left {
  left: 0;
  background: url("https://images.unsplash.com/photo-1635048438162-7a31e9648949?ixlib=rb-1.2.1&ixid=MnwxMjA3fDB8MHxwaG90by1wYWdlfHx8fGVufDB8fHx8&auto=format&fit=crop&w=327&q=80");
  background-repeat: no-repeat;
  background-size: cover;
}

.split.left::before {
  content: "";
  position: absolute;
  width: 100%;
  height: 100%;
  background-color: var(--left-bg-color);
}

.split.right {
  right: 0;
  background: url("https://images.unsplash.com/photo-1621259181233-aa03cf592ea7?ixlib=rb-1.2.1&ixid=MnwxMjA3fDB8MHxwaG90by1wYWdlfHx8fGVufDB8fHx8&auto=format&fit=crop&w=429&q=80");
  background-repeat: no-repeat;
  background-size: cover;
}

.split.left::before,
.split.right::before {
  content: "";
  position: absolute;
  width: 100%;
  height: 100%;
}

.split.left::before {
  background-color: var(--left-bg-color);
}
.split.right::before {
  background-color: var(--right-bg-color);
}

.hover-left .left {
  width: var(--hover-width);
}

.hover-left .right {
  width: var(--other-width);
}
.hover-right .right {
  width: var(--hover-width);
}

.hover-right .left {
  width: var(--other-width);
}

@media screen and (max-width: 800px) {
  h1 {
    font-size: 2rem;
  }

  .btn {
    padding: 1.2rem;
    width: 12rem;
  }
}