Astyanax is a side-scrolling platform action game set in a fantasy world. The hero sets out to slay the evil wizard terrorizing the land. He is armed with an ax and also has a magic lightning spell that can be powered-up two times. Magic upgrades and health potions can be found in small stone pillars. The player needs to beat monsters in a number of locales, jumping across pits and fighting bosses at the end of stages. Two-palyer co-op is supported, with the second player being palette-swap of Player 1.

The game was designed by Tokuhiro Takemori who previously worked on Legendary Axe, and the basic game mechanic is similar -- in order to deal heavy blow with the axe the player needs to stop swinging it for a while. The NES version released after the Arcade game, while generally having same gameplay, features completely different level layouts, enemy designs and story.