App.vue

<template>
    <div id="app">
        <div id="game">
            <Game />
        </div>
        <div id="border" />
        <div id="input">
            <Chat />
        </div>
    </div>
</template>

<script>
import Chat from './components/Chat.vue'
import Game from './components/Game.vue'

export default {
  name: 'App',
  components: {
    Chat,
    Game
  }
}
</script>

<style>
    #app {
        font-family: 'Trebuchet MS';
        text-align: left;
        background-color: black;
        color: cyan;
        display: flex;
    }
    #game {
        width: 50vw;
        height: 100vh;
    }
    #input {
        width: 50vw;
        height: 100vh;
    }
    #border {
        border-right: 2px solid cyan;
    }
    @media (max-width: 1000px) {
        #app {
            flex-direction: column;
        }
        #game {
            width: 100vw;
            height: 50vh;
        }
        #input {
            width: 100vw;
            height: 50vh;
        }
    }
</style>