I'm stuck!

So a few days ago I was listening to the song "I Ran So Far Away" by A Flock of Seagulls, and he kept saying "I ran" and that made me think of Iran, which made me think of guns, which made me think of "Machine gun man" (it rhymes with I ran :p) and so I decided to make a game where you run around and shoot people. Ok, I did that. You run around, you shoot stuff, blood flys out and stains the ground. That was fun for like....10 seconds. Now I don't know what to do to make it into a real game :( The way it is now, you can run around in the level, each level has a few spawn points for enemies that makes new enemies every so often. The entire level fits on the screen, so you can see all of it at one time. Each level has one exit point, which if you get to you leave the level and go to the next level, provided there is another level to go to. So basically you run around, shoot stuff, go to the exit, go the level 2, shoot stuff, go to the exit, and beat the game (I haven't made more levels yet) So far, the enemies just...uh...move towards you and get shot. They die in one hit. They're just there so you can spray blood everywhere. So, really, I don't know where to go with this game. I could make the levels bigger, and add vehicles. Seemed to work for UT2004 :p. But it still wouldn't be a game. There is like...nothing to do but shoot people and go to the next level and shoot the same stuff again. Should I make stats scriptable enemies that actually do stuff? Add new weapons? Multiplayer (Don't know how to do that, internet is hard) I was thinking of maybe adding some kind of jewels to the game, you have to run around, collect jewels and then the exit would be revealed. Enemies would be harder to kill and levels would be bigger with more diverse elements than "solid quads" (squares on the map that you can't walk through) and "non-solid quads" (squares you can walk through). I don't know, any ideas on how I could make this into a real game? By the way: Level One Killing Level Two Killing