The theme of Wizball is unique. It is a horizontally-scrolling game, which involves navigating around a landscape and shooting at sprites. However, the aim of the game is to collect droplets of coloured paint to colour the level. Each level starts off as monochromatic, drawn in three shades of grey, and needs three colours to be collected to complete it.
It was actually my friend that discovered the secret behind Wizball, that you should collect droplets and paint the world around you. It was after that discovery that we played it like maniacs, trying to solve the mystery.
We never did. Yet, this is a very amusing and curious game. It is like nothing I've ever seen since and should be experienced by any serious gamer.