LED Bulb Brightness vs. Room Size Calculator 

LED Bulb Brightness vs. Room Size Calculator .calculator { max-width: 500px; margin: auto; background: #fff; padding: 25px; border-radius: 10px; box-shadow: 0 4px 8px rgba(0,0,0,0.1); } h2 { text-align: center; color: #333; } label { display: block; margin: 15px 0 5px; } input, select, button {...