*{box-sizing:border-box;margin:0;padding:0}.app-container{display:flex;flex-direction:column;align-items:center;justify-content:center;height:100vh;background-color:var(--background-color);color:var(--text-color);transition:background-color .5s,color .5s}.app-container.light{--background-color: white;--text-color: black}.app-container.dark{--background-color: black;--text-color: white}h1{font-size:2rem;margin-bottom:1rem}button{padding:.5rem 1rem;margin:.5rem;border:none;border-radius:5px;cursor:pointer;transition:background-color .3s,color .3s}button:hover{background-color:var(--hover-background-color);color:var(--hover-text-color)}