I love the game "Castle Crashers." My idea comes from this level from the game.
https://www.youtube.com/watch?v=fwrwO3eNAQo
Replace the giant troll with a dog, and the Knight on the deer with a cat on a spaceship and you get the general idea. However I plan to extend on this basic idea. The goal is to get to a mouse that you, the cat, are chasing while collecting space catnip along the way. You must avoid getting knocked towards the dog and get eaten, while trying to catch the mouse and eat it. You move faster than the dog, who moves faster than the mouse, so as time progresses, the distance between the dog and mouse and therefore the room for error decreases. You move faster than the dog, but only if you don't get knocked back.
The more catnip collected, the higher the score. The game ends when either you catch the mouse or the dog catches you. You get bonus points if you catch the mouse, and you get more the quicker you do it.
Obstacles include balls of yarn, which stop you momentarily while you play with them, but gain you points, asteroids, which knock you back, and spaceships, which have the same effect but are moving obstacles.[youtube][/youtube]
https://www.youtube.com/watch?v=fwrwO3eNAQo
Replace the giant troll with a dog, and the Knight on the deer with a cat on a spaceship and you get the general idea. However I plan to extend on this basic idea. The goal is to get to a mouse that you, the cat, are chasing while collecting space catnip along the way. You must avoid getting knocked towards the dog and get eaten, while trying to catch the mouse and eat it. You move faster than the dog, who moves faster than the mouse, so as time progresses, the distance between the dog and mouse and therefore the room for error decreases. You move faster than the dog, but only if you don't get knocked back.
The more catnip collected, the higher the score. The game ends when either you catch the mouse or the dog catches you. You get bonus points if you catch the mouse, and you get more the quicker you do it.
Obstacles include balls of yarn, which stop you momentarily while you play with them, but gain you points, asteroids, which knock you back, and spaceships, which have the same effect but are moving obstacles.[youtube][/youtube]
I do love Castle Crashes too, I can't wait to see the final product (if it'll ever come of course) 
