The gameplay is different from the original Galaga, it adds dimensons, big Galagas carring small Galagas, obstacles to destroy, and differnent bosses in different dimensons.
To advance through the dimensons, the player must first get 2 blue capsules, and then complete the bonus stage. When the bonus stage is complete, 2 blue capsules will rise to the air, opening the portal to the next dimension, awarding the player 10,000, 20,000 , etc.
Capsules were also added to Galaga '88. There are 2 kinds of capsules, a blue one, and a red one.
These capsules are used to advance to the next dimenson. They can be obtained by destroying certain obstacles, or by destroying the 2 galagas that make a giant bug which fly left and right going down. The only way to advance to the next dimenson is to get 2 blue capsules. After the challenging stage is done. The 2 blue capsules will rise in the air, opening the portal to the next dimension and awarding the player the amount of points every 10,000. If the player has only one blue capsule then it will fly into the air and disappear. On Galaga '88, there are a total of 5 dimensions. On Galaga '90 there are a total of 4 dimensions.
These capsules are used to upgrade your ship. If your ship is a single ship, it will become a dual ship. If your ship is a dual ship, it will turn into the new triple ship which can fire three bullets at the same time, but will become a dual ship again if hit by an enemy or shot by an enemy. You also get 500 points when you get a red capsule. If you collect a red capsule while your ship is a triple ship, you only get 500 points.