I like the "Do Not Sleep" functionality a lot. However it would be great to allow the screen to idle sleep while still preventing the system from idle sleeping. I don't know if your tool is using caffeinate to do it's job, but what it does is very similar to a 'caffeinate -d'. I would prefer something that behaves like 'caffeinate -i' which is what I usually type in the console. In situations where you want to prevent system idle sleep to perform a long running background task, keeping the screen on is useless (and you probably *want* it to idle sleep).