If you like using your Mac in bed at night or find the screen is straining your eyes, you could benefit from dimming the screen.
Normally you have to go into your Mac's screen settings to do this but Blackout allows you to do so instantly from your menu bar with much greater control. The highlight of Blackout is a spotlight feature, which allows you to shine a light on any part of the screen in the same way that a spotlight is used on a stage. You can toggle the opacity of the background using a slider bar in the middle of the screen. The good thing is that Blackout doesn't alter any of your screen settings so as soon as you go to your menu bar to toggle it on or off, you return to normal instantly. There are also other effects you can apply such as soft edges and fading displays instead of the spotlight. It depends on your preferences, your external light, and what you are reading which you'll like best. It can be a little tricky to access the Blackout settings however to change between the different modes and a nice 'Settings' option in the menu bar would have been preferable.
If you like reading on your Mac screen at night or want more control over your brightness settings, Blackout is a flexible and effective application.