Pulsar

In Pulsar, you control a tank in a constantly shifting maze. Your goal is to collect colored keys to open locks that give you access to new areas of the maze, while avoiding enemy aggressors and not running out of fuel.

In each level of the game, you start in the bottom left of the maze. The door, allowing egress from the level, is on the bottom right along with a set of colored and numbered locks. The keys to these locks can be found along the top wall of the maze. Only one key can be transported at a time, and while it is being carried, the tank changes color to match that key. Gameplay then involves navigating the maze, collecting the keys, activating the locks, and moving to the next area. Bonus points are doubled at the completion of a level if the locks are deactivated in numerical order.

Of course there are added difficulties. For a start, the walls randomly move so that you may need to choose a different path to reach a key. If you hesitate, randomly appearing force-fields can destroy stationary tanks. You also have a limited amount of fuel, which depletes at a slow but relentless rate. There are also several types of alien aggressors with different movement patterns, which can shoot you or collide with you if you are too careless. Amongst the aggressors is the large, slow and erratically moving "pulsar" which takes many shots to destroy, after which it splits into six smaller aggressors. Shooting any of these alien craft will replenish some of your fuel.

Later levels become more difficult in several ways. The aggressors get faster and shoot more frequently, the maze shifts more rapidly, and extra keys (up to five) may be required before you can escape from this part of the maze. Points are earned for shooting aliens, and bonus points are earned at the end of the level for the amount of fuel remaining. You start the game with 2 to 5 lives (depending on settings), and play continues until they are all lost.