Only use this for 180 seconds. When you open this page, the default 670nm color is displayed. If you select the gradient color option there is a subtle shift between red colors moving between 5 color steps. You'll probably not notice the difference... but the base color is: 670nm (used in the study) Then I add 4 super slight variations: 704nm, 705nm, 707nm, 709nm If there is interest, I will add functionality: the ability to select color stepping HSL color profile along with any good ideas... Keyboard commands: F for full screen, C for gradient, T for 3 minute timer. Email me