Part 1 - Basic styling of our app

App.scss

.App {
  position: relative;
}

.full-width {
  max-width: 480px;
  width: 100vw;
}

.cover {
  position: relative;
  width: 100%;
  background-position: center;
  background-size: cover;
}

.page {
  position: absolute;
  top: 0;
  display: flex;
  justify-content: center;
  min-height: 100vh;
}

h1.title {
  position: relative;
  z-index: 10;
  margin: 0;
  margin: 50px 20px;
  width: 70%;
  color: #fff;
  font-size: 3em;
  line-height: 0.9;
}

index.scss

html {
  margin: 0;
  padding: 0;
}

body {
  margin: 0 auto;
  padding: 0;
  min-height: 100vh;
  max-width: 480px;
  width: 100vw;
  background: #fff;
  font-family: system-ui;
}

* {
  box-sizing: border-box;

  -webkit-tap-highlight-color: rgba(0, 0, 0, 0);
}

List.scss

.page-list {
  .list {
    display: flex;
    flex-direction: column;
    padding: 50px 20px;
    width: 100%;
  }

  .preview {
    display: flex;
    align-items: flex-end;
    flex-basis: 440px;
    flex-shrink: 0;
    margin: 15px 0;
    border-radius: 16px;
    box-shadow: 0 0 50px rgba(0, 0, 0, 0.2);
    cursor: pointer;

    user-select: none;
  }
}

Post.scss

.page-post .post {
  position: absolute;
  top: 0;
  z-index: 100;
  width: 100%;
  height: 100vh;
  background: #fff;
  transition: box-shadow 350ms ease;

  .cover-wrapper {
    position: absolute;
    top: 0;
    left: 0;
    z-index: 10;
    display: flex;
    overflow: hidden;
    align-items: flex-end;
    max-height: 64vh;
    width: 100%;
    height: 100%;

    .cover {
      position: absolute;
      top: 0;
      left: 0;
      height: 100%;
    }
  }

  .content {
    position: absolute;
    top: 64%;
    margin-left: 50%;
    padding: 20px;
    background: #fff;
    line-height: 1.8;
    transition: opacity 800ms 200ms ease;
    transform: translateX(-50%);
  }
}

.page-post {
  .close {
    position: fixed;
    top: 20px;
    z-index: 1000;
    margin-left: 20px;
    width: 36px;
    height: 36px;
    border-radius: 18px;
    background: #fff;
    opacity: 0.7;
    cursor: pointer;
    transition: opacity 350ms ease;
    &::after,
    &::before {
      position: absolute;
      top: 17px;
      left: 8px;
      width: 20px;
      height: 3px;
      border-radius: 1.5px;
      background: #000;
      content: '';
      transform: rotateZ(45deg);
    }
    &::before {
      transform: rotateZ(-45deg);
    }
  }
}