Hard 'n' Heavy is a platformer game where you control a robot named 'Heavy' or 'Metal', who must run through five side-scrolling worlds, avoiding enemies and collecting power-ups and diamonds along the way. The game features an upgradable weapons system using bouncing balls and flamethrowers to defeat enemies, as well as two-player co-op mode.
The gameplay involves jumping, running, and shooting your way through levels, with the goal of reaching the end of each world while avoiding obstacles and enemies. Collecting extra lives and diamonds will earn you bonuses, including extra lives and access to secret zones. Each world has a final boss monster that must be defeated before progressing.