discourse/app/assets/stylesheets/mobile/emoji.scss

.emoji-picker {
  border: none;
  position: fixed;
  width: 100%;
  max-width: 100vh;
  top: 0;
  left: 0;
  border-bottom: 1px solid var(--primary-low);
  min-height: 50vh;
  .emoji-picker-emoji-area {
    img.emoji {
      // custom emojis might import images of various sizes
      // we don't want them to be deformed in the picker
      width: 28px !important;
      height: 28px !important;
    }
  }
}