taro/src/app.scss

/* #ifdef weapp */ 
page {
    background-color: #000;
}

@media (prefers-color-scheme:dark) {
    page {
        background-color: #000;
    }
}

.container{
    display: flex;
    flex-direction: column;
    flex: 1;
    background-color: #000;
    height: 100vh;
    width: 100vw;
}
/* #endif */