main { position: relative; } body { background: none; } body::before { content: ""; position: absolute; top: 0; left: 0; width: 100%; height: 100%; background-image: url("../img/rough_bg.jpg"); } body.dark { color: #fff; } body.dark::before { filter: invert(1); } .dark main { background: #222227; } .dark .dayName { color: #ddd; background-color: #444; } .dark .dayTime { color: #ccc; background-color: #333; } .dark .day { border-left-color: #111; }