Alien Slingshot is just a simple game in which you control a rocket and you need to destroy as many alien ships as possible in order to save the planet. For every alien ship you destroy you will be given points. To move your rocket, you need to click and pull back your mouse, and then choose the desired direction and intensity of the shot. The alien ships will continually fall from the sky, so you may hit more than one with one shot. You have three lives, and you may lose them if you don't hit anything with your shot. From time to time, bonus points and power-ups will fall from the sky, and you can get them by hitting them with your rocket.
The game has a very similar gameplay to Rocket Upgrade, but in the latter the controls were erratic. In this game, fortunately, they work just fine. The game includes four different levels with different themes, which you will see as you advance in the game. As you can see, graphics are simple, but cute, there are only sounds when you launch the rocket, and the music is annoying, but you can mute it from the main menu.
To sum up, Alien Slingshot is just a simple and silly game to pass the time, which may work for little kids, but I wouldn't recommend it for adults.