Designing a shoot ’em up is in theory quite simple. So long as the player has a ready supply of missiles and enemies to gun down he is going to be happy. But when you start to analyse the game’s design and requirements in more detail you can see a little bit more.
I have pretty much decided that the game works best when I throw up a challenge (e.g. shoot the alien), offer a reward (catch the falling points bonuses) and then immediately throw in something to thwart it. By offering this challenge vs reward vs added challenge to the game I am sure to make it more interesting.
The kind of added challenge I’m thinking of can be as basic as the aliens littering the screen with bombs. The player shoots an alien, the alien yields a bonus but the player has to navigate his way inbetween the bombs to get to the goods.
On later levels this can be quite tricky so to further give the player a fighting chance I decided to implement a limited means of clearing the canvas of bombs. By hitting the smart bomb button the screen flashes and all enemy bombs are gone thus clearing the way for the player to collect goodies or evade certain doom. Naturally smart bombs are limited but in keeping with the design ethos I also created a Smart Bomb power up that falls down the screen much like other power ups.
So just now the player has complete control of his ship’s missiles, speed and bomb ability. By carefully controlling each the player is equipped to compete.
The aliens that dive leave sticky gunk on the floor. If the player ship moves through this it’s speed is halved leaving it much more vulnerable to attack. So by shooting the falling aliens the player maintains his ability to compete in the game. As a reward a shot on the falling aliens yields twice their points score.
The mid-level boss that appears once every 4 levels or so employs the same approach. The player must ensure that the bus makes it to safety but the bus is capable of getting stuck in the goo just like the player. The boss will only shoot if it falls within radar (as indicated by the red strip on screen) so the player must rapidly shoot the alien to keep it above the line whilst the bus passes beneath. The rewards for shooting the boss needed to be plentiful so I first bounced it with every strike, then spawned a smoke cloud and finally chipped away at the visual health bar at the top of the screen. By the time the boss is defeated the player is satsified that his hard work has been worth it and hopefully his score reflects the safe passage of the bus on more than one occassion.
Balancing game elements is fun. Since everything is defined with variables and numbers balancing is pretty much a game of finding the right combinations of numbers.