Shamus is a Shoot'em Up game that follows the story of Shamus, who must infiltrate the lair of the elusive Shadow and stop him from causing harm. The player will have to navigate through over 120 rooms, avoiding the Shadow's robotic minions and avoiding electric walls while searching for keys to unlock locked doors.
The gameplay involves shooting and sneaking past enemies, with the added challenge of random respawning after re-entering a room. The game is divided into four levels, each with its own set of challenges and obstacles. The player must be careful not to get caught by the Shadow or his bulletproof versions that appear at certain times.