Eight, while the Outer Regions' is the "dark side" of the lunar body in Wave Three. Gameplay Enemies and credits Enemies are destroyed purely for money. Most enemies move in pre-determined paths. Some enemies will try to crash into the player. Turrets also aim to hit the player. There are no obstacles to avoid (except the enemy ships themselves). While flying enemies are the most numerous, many ground targets (buildings, ships, vehicles, turrets) can be destroyed as well. Bosses appear at the end of each wave or even halfway through the later, more difficult waves. In the Outer Regions, the bosses are ground bases where the player has to take out their various component weapons. For each target destroyed the player earns credits. The amount of credits earned per enemy destroyed is usually proportional to how tough or dangerous it is, with some of them dropping additional credit bonuses. The Raptor jet is particularly durable compared to player-controlled craft of other scrolling shooters, which can be destroyed with a few hits. However, there are no "lives" so the game is over when the player dies, although the player can reload a recently saved game. The player can decide to end a level prematurely, in which case they will lose all the money acquired since starting the level. Damage sustained will remain though, as will collected weapons - as such, one technique to rapidly collect money is to start a level that has an expensive, collectible weapon at the start, collect the weapon, quit and start over. After a couple dozen iterations or so, selling the gathered weapons will provide enough cash to buy most "equipped" weapons, at least the basic auto-tracking turret, and a couple of phase shields - enough to handle most levels as a Rookie. Weapons and shields The player (there are four playable characters) starts out with only the default machine guns, and will eventually be able to buy or collect more weapons using a credit and purchase system menu before starting or after finishing a wave. There are two major categories of weapons: the first type is always active (all carried weapons of this type will always fire simultaneously whenever the player shoots), and the second type is selectable. During gameplay, when firing, only the currently selected selectable weapon will fire, though the currently selected weapon can be dynamically switched to deal with the appropriate situation.