Vice: Project Doom, released in Japan as Gun-Dec (ガンデック), is a multi-genre action game developed by Aicom and published by Sammy for the Nintendo Entertainment System in 1991. It is a side-scrolling platform game similarly to the Ninja Gaiden series for the NES, with the addition of gun shooting and driving segments as well. The player takes control of a secret agent who must uncover a conspiracy involving a new kind of alien substance.

Vice: Project Doom consists of 11 stages. The very first level, as well as Stage 10, are driving stages, while Stage 4-2 and 11-1 are shooting stages; the rest are standard side-scrolling stages. Each begins with a cinema-style sequence which provides the game's narrative. As usual of the genre, the player has a health gauge and a limited number of lives. Unlimited continues are provided as well.

In the main stages, Hart can switch between one of three weapons: a Laser whip, a .44 Magnum revolver, and a supply of Stick hand grenades. The laser whip is a short-range weapon that can be used infinitely, while bullets and grenades are limited and must be replenished by picking additional supplies dropped by defeated enemies. Other power-ups includes health-restoring heal-aids and meat, as well as coins that will give the player one extra lives for every 100th one collected. In the main segments, Hart can jump, attack, crouch, and climb ladders like in most other action games. He can also run while crouching. In the vehicle stages, the action is viewed from an overhead perspective, as the player's maneuvers Hart's car through the road while shifting between three gears and shooting at enemy vehicles with the car's equipped gun. In the shooting segment, the action is viewed from Hart's perspective, the player moves the target indicator around the moving scenery, shooting the gun with one button and tossing grenades with the other.