Runs pretty smoothly here - maybe it's your browser/system?
var default_settings = { brightness: 2.7, saturation: 1.4, lamps: 5, block_size: 40, update_interval: 500, fade_time: 400 };
var default_settings = { brightness: 2.7, saturation: 1.4, lamps: 5, block_size: 40, update_interval: 500, fade_time: 400 };