Bubble Bobble has been my favourite computer game for close to 25 years now. I first encountered it at youth club when I was around 10 years old, and straight away I was enthralled. When my own 10p coins had been exhausted, I would stand around the cabinet and watch other (better) players have their turn. The appeal was obvious: it was colourful, simple to play, had a host of powerups and was, of course, two player. It's also a game where even a very poor gamer can advance a few levels before using their lives, and one where progress is initially quite easy, so there's a good sense of accomplishment on each repeat play. The premise is simple: you're a man turned into a dragon and your girlfriend has been kidnapped. You have to fight your way through lots of screens to win her back. You can blow bubbles to trap enemies and then pop them to defeat the enemies. When all the enemies have been cleared from a screen, you advance to the next screen. The enemies vary from level to level, with the enemies becoming harder or more numerous as the game progresses. From little clockwork demons that jump between platforms, to little drunk imps that throw things at you and invaders who rain destruction from above. Fortunately, there are a variety of powerups to aid you in your quest: sweets, to enhance your bubble blowing ability; shoes to help you run faster; umbrellas to skip levels, and more besides. One of the things I like about Bubble Bobble is that it uses counters to keep track of the availability of powerups. This means that the appearance of a power up is, at least partly, in the player's control. The appearance of powerups might seem random, but it's not. It's all to do with the game keeping track of various metrics. The yellow sweet appears when the player has made his character jump 51 times; the orange umbrella appears when the player has popped 15 water bubbles, and so on. This system gives the player an incentive to do more than the minimum required to complete each level; it encourages movement and chasing down bubbles to pop. It also means that the developer can limit how frequently or how soon a powerup appears. With a random number system you could get two bonus items appear in quick succession, or very shortly after the start of the game, or you could have a long time between powerups. With this system you have them appear after a certain amount of interaction. The main reason that Bubble Bobble remains my favourite game is that it's just so easy to pick up, play for a little while and put down again. It's also easy to introduce a friend to. There are no special button combinations to learn, there are no special weapons whose function needs to be worked out, no puzzle element to overcome, just good, honest, running, jumping, bubbling fun.