Birdie is part flight simulator, part exploration game. The player controls Birdie, a white bird of unknown species. The game starts in a forest where the player can practice flying (there is no danger there except for other birds if Birdie flies too high for too long). Avian flight dynamics are modelled quite well (wings must be beat at a regular rythm to avoid stalling, speed is gained by diving). Butterflies can be picked up for an energy boost (but too much eating and Birdie becomes aggressive and hard to control). Scattered in the forest are Magic Doors which lead to several surreal landscapes, peopled by all manners of bizarre creatures (the manual hints that these may be what a bird's dreams are like).
There is no definite ending in this game, the player can keep exploring the game as long as Birdie can be kept alive.