Bobby Jenkins lives next door to Leon, a scientist on the verge of discovering a device that can stabilize and control portals to connect planets across multiple universes. During his experiments, Leon is transported to a weird dimension where the evil Looger and his cohorts steal the portal travel technology and use it to break into our world to perfect the technology. Once here, they are discovered by Bobby who is captured and questioned about Leon’s work. Bobby manages to escape and is teleported to their world where the story takes place.
Scaler is an action platform game in which the player controls Bobby Jenkins, who turns into a lizard in the "bizarre dimension" and tries to stop the evil Looger and his cronies. The player can use various abilities such as climbing walls to reach new areas, riding vines to charge up electric bomb attacks, and using camouflage to sneak by deadly traps. Scaler's attacks include his tongue or claws, which can be upgraded during the game. The Electric Bomb attack hits several enemies at once. By defeating certain enemies, Scaler can transform into them and use their special abilities.
The player can break open cocoons and shells to collect Klokkies and Crystal Gems, which are used to get new abilities and upgrade existing ones. Collecting 100 Crystal Gems results in an alternate ending. Gathering Lizard Eggs unlocks more levels and prevents Looger from mutating them into monsters. The game also features a picture gallery where the player can view additional pictures as they accumulate Crystal Gems.