* { box-sizing: border-box }

body { margin: 0 }

.outer-scroll {

  width: 100vw;

  height: 100vh;

  overflow-x: auto;

  overflow-y: hidden;

  border: 2px solid red;

}

.inner-scroll {

  width: 200vw;

  height: 100%;

  overflow-x: hidden;

  overflow-y: auto;

  background: linear-gradient(0.25turn, #3f87a6, #ebf8e1);

}

.content {

  width: 300px;

  height: 200vh;

  background: linear-gradient(#e66465, #9198e5);;

}