Crossdressing Lizard Unleashed

Background: 

I made this little game as part of a rapid prototyping course. We had a week to hand in a complete game (meaning: start screen, game loop, win and game over condition + screen) with only three constrictions: We had to use Pico-8, we had to generate a random game name with the videogamena.me generator, hence the origin of the title: Crossdressing Lizard Unleashed, and we were only allowed to use one screen in Pico-8, no scrolling. 
I didn't have any prior programming experience, so basically Lua has been the first programming language I have really used. This is the result of 5 days of learning.

Game: 
You play as the Crossdressing Lizard, who has escpaded from its cell in the zoo but still has to find its way past the zoo guardians and out of the zoo itself. 

Mechanics: 
Use the arrow keys to avoid the enemies and escape through the doors, which open up one at a time at the side of the screen. 
To confuse your enemies, you can change your clothing to match the color of the zoos floor. They will have trouble following you then. 

State of the prototype: 
Because I knew I didn't have that much time for this, I didn't plan too much and got most of my ideas in the game. What I couldn't really get to work though was making the escape doors randomly appear so the gameplay is always different. The second enemy's movement is also still hardcoded to the current location and appearance time frame of the doors, so that would have to change also. 
Other then that I'd thought of adding obstactles or other level elements, that would give the game a more labyrinth feeling in later levels, but I don't really know how to program the enemies for this case. Right now they are just following the doors or the player character, that's all they do. 

If you have any thoughts, suggestions or ideas of how to continue or improve my little escape game, I'd love to hear it.