Flying Monkey Game

Jeffrey and I are working together to make our first game. Both of us want to contribute as a programmer, however as artist is as important as programmer and I can't draw so Jeffrey agreed on the drawing job. In our first meeting, we talked about ideas, what we should do, what our game should be and I wanted to create a game about a monkey, because this year is a Monkey year. At first, I just want to create some random monkey climbing around in the jungle, avoiding danger and taking objectives. Then Jeffrey thought it would be great if we have a flying monkey riding a jet pack with a gun, shooting enemies with bananas so we came up with this game: Flying Monkey.
My role is to create interaction with all the characters, we planned to make it endless run and random spiders or snakes would appear and we have to avoid it or shoot it down, but I have not figure out how to create random stuff and endless room. Therefore for our first playable, I just made one simple game with five big black spider running around in a simple path, our monkey can shoot them down to pick up the giant banana and win the game. Here is the link to our first playable ever: link.
My main question is should I create a fence around the room, that limits our monkey's movement, I think that would be create, and easier to show that spider crawl up and down from there. We will develop the game more and more, and will come up with a better version of Flying Monkey soon.