Alien Shooter is a 2D platformer game made in Unity 3D engine using C# scripting. It is a single player game where waves of enemies spawn to kill the player. The player defends himself with a weapon. A* Pathfinding algorithm was used to make the enemy AI. It was based on mechanics of games such as Super Mario Bros. and Contra. Making a game of platform genre that has engaging premise was the objective of the project. The game has been described thoroughly in this document including the major classes. The functional and non-functional requirements are given. The system design is explained. Class diagram and state diagram give a general picture of the working mechanics of the game. Corrective maintenance of the game will be carried out.