What you'll need is an ego drawn from the top-down. Simple enough.
You'll need at least one enemy view, too.
Then you'll need a view that represents a bullet.
You'll need to distance(bullet, enemy, range) for each enemy on the screen.
Then you'll need to have a piece of code that starts the bullet when a key is pressed (f10 is just about the only "free" control key) from the ego's current position (draw(bullet); set.dir(bullet, ego_dir); ) and continue until it hits an enemy (if range<=10 for instance), or goes off screen (if(bulletx<1 || bulletx>120 || bullety<1 || bullety>150) or something... not too sure about the maximum x or y). if range<=10, then switch the enemy loop to a death-loop (set.view(enemy, death_loop)) and run it to the end of the loop (end.of.loop(enemy, done_flag)), then (erase(enemy)).
You're kind of limited to the number of objects on screen, and you can expect slow-down if you approach the maximum number.