prototype4 is a retro-looking arcade space shooter. The game can be played on your web browser or you can download it on your Mac from the Mac App Store. This game, like other shooters, is all about killing wave after wave of enemies while staying alive. The enemy ships come from the top of the screen, and you have freedom to move around the screen as you like, but you can only shoot upwards. Both the enemy ships and your ship are made out of triangles and other shapes. Your weapons and the enemy's are made with particle effects, so the screen will often look like a collection of dots and squares, especially when there are many enemies on it at the same time.
prototype4 lets you play in four different difficulty modes: easy, normal, hard and ultra. The easy mode is fun to play but it can get messy when there are many enemies on the screen. It is often hard to see what is going on with any clarity. The ultra mode, on the other hand, isn't too much harder than the easy one, but the enemies move faster and you have less energy, so a couple of hits will destroy your ship.
In conclusion, prototype4 is a nice arcade game for some casual playing. There is really no replay value in it and it can get boring after a while. The graphics are simple and don't really help to make the game more attractive.