Thinking of an idea

My first idea was to create a game that was similar to snake, but I thought that it would be difficult to incorporate any A.I. into that, so I thought of something else. I thought of a game with the orientation being looking down on the player. It would consist of a spaceship (The player would control this) and it would be positioned in the centre of the screen. The player would be able to rotate and shoot from the front of the spaceship. A.I. enemies would come towards the player and try to shoot and kill it. The A.I. properties of the enemies would consist of larger amounts of enemies attacking the player as time went on, the enemies could try and avoid the bullets the player would shoot, but not too much so that it would be difficult - just enough to make it fun. Some enemies would also be "tougher" than others, meaning it would take more shots to kill those enemies, this would make it harder.