Scope is a Sega Master System homebrew game by 64kb Games.

How good is your reaction time? Scope is a very simple light-phaser game that lets you test your speed and accuracy. A picture is placed on the screen. Only the bar where you are aiming is illuminated with color. You only have 3 seconds to find the bright red color on the screen and shoot it!!! If you hit, the whole picture is shown in color before going on to the next picture. Miss even once, and you get sent back to the title screen. Hit all 20 targets, and your reaction time is measured at the end of the game. How quick are you on the draw?