The gameplay of the 1999 edition is very similar to most versions of Space Invaders. The player controls a tank which can move left and right, and fires a single missile when the fire button is pressed. The alt-fire button will fire a special missile if the player has hit four alike aliens in a row. Each level presents an arrangement of aliens which start moving slowly from one side of the screen to the other, moving down slightly whenever they reach the right or left. The player must destroy all the aliens before they reach the bottom, while avoiding their bombs. If the aliens do reach the bottom, they will swoop onto the player's tank, destroying it. If the player has any lives left the aliens will move halfway up the screen and the player can continue to try and destroy them. Throughout each level, a number of mother ships may fly across the top of the screen. These mother ships pose no danger to the player, but drop numerous power-ups when hit;
Shield, which covers the player's tank in a shield, saving them from most attacks - but only once.
Double Shot, which allows the player to fire one extra missile quickly after their first, so that two may be on screen at a time instead of one. It is very useful for bosses.
Time Stop, which freezes all aliens and bombs for a few seconds, making them easy targets for the player.
Max Energy, which grants the player the special missile associated with the last type of alien they hit. If the player has an empty energy bar, the power-up grants the player that level's special alien's missile.
If a player loses a life, their double shot power-up will become inactive and their energy bar will be emptied.
Players can save their progress at any point.