Metal Slug Advance

Metal Slug Advance is a run and gun video game for the Game Boy Advance handheld system created by SNK Playmore in 2004, and is canon to the Metal Slug series. It is notable as the only Metal Slug video game not to feature Marco Rossi as a playable character. In this context, "slug" refers to a tank.

Storyline
A survival training camp for new Peregrine Falcon recruits has just begun, where the recruits must survive on an unnamed island with limited supplies and weaponry. However, a large blimp begins to hover above the island, as General Morden's troops parachute down and attempt to build a new base, while successfully capturing many of the new recruits. Players play as either new recruits Walter Ryan or Tyra Elson as the survival training soon becomes a full-fledged assignment for the remaining recruits as they pierce through enemy lines.

Gameplay
The gameplay is very similar to any other Metal Slug game, but with two new systems; the life system, and the card system. The life system is simply a life bar for players, as it replaces the extra lives from all the other Metal Slug games. As players take damage, the life bar depletes (different attacks cause different amounts of damage). Collecting food items can restore health, and players instantly die from being crushed, or falling down a pit. The Card system is a card collecting part of the game. Cards can be found from shooting certain parts of the background, and by obtaining it from certain hostages, and sometimes by doing both. The cards have many different purposes, from giving detailed info on items and characters from the Metal Slug series to boosting player abilities, and even unlocking special (and new) slugs. There are 100 cards to collect, and collecting them all becomes the main objective to anyone who defeats the final boss.

Vehicles
The Metal Slug, the Slug Flyer, and the Slug Gunner (as an unlockable) make a return in the game. There are also two new slugs which are simply Metal Slug modifications.

Slug Type-R
A light-brown Metal Slug which fires the vulcan gun tandem the direction the player is (except vertically). This type of vulcan is the same as the Metal Slug Type-R in Metal Slug 3. The Slug in Metal Slug Advance is not the same, however, as the agile, golden Metal Slug in Metal Slug X (which had a normal vulcan). Type-R must be unlocked in order to be used.

Black Hound Slug
A black Metal Slug that was a secret boss in Metal Slug 5. It has a painted "Devil's Eye" on the side, and a bazooka replacing the vulcan gun. However, this version of the slug has lost its arcing laser attack, and replaced the RPGs it shot from the bazooka with black enemy chasers. It has a firing delay of about half a second. Like the Type-R, It must be unlocked in order to be used.

The Slug Mariner was planned for the game, as well as an underwater level, but was removed in the final product (Game hackers can still find the Slug Mariner with the proper programming needed for it to be used in the game).