Players start from the middle of the Defender Base level 1 with 3 lives. 30 Alien Ships are deployed at the Alien Base level (level 8) into 3 rows. These 30 Aliens Ships make up the 1st Wave. Once they are destroyed a new Wave is deployed.
One to three Players can play at the same time. With 3 new Players gaming one Wave takes about 30 minutes, Players can usually complete 2-3 Waves.
Ten-sided dices are used.
Picture 1. The starting positions. 3 Players are lined up at the Defender Base level 1, Aliens are lined up at their Base level and an Alien Mothership is at stand-by at the level 9.
Game proceeds as follows: 1st Player moves and shoots, Aliens move, 2nd Player moves and shoots, Aliens move, etc. This means that in a 3 Player game the Aliens move 3 times before the Players next turn comes.
A Player can move a total of 10" on his turn. Sideways movement is done in 1" intervals. Player can also move between Defender Base level 1 and 2, this costs 3" of movement. Movement can be devided into several parts, i.e. Player can move-shoot-move-shoot-shoot-move, etc.
A Player can shoot during his turn as long as he scores hits. Once a shot misses, the Player's turn ends. Player's turn ends also if he just says so (e.g. Player doesn't have targets and doesn't want to move).
To shoot Player rolls 1D10. The required number depends on the distance between the Player and the target. To hit an Alien at level 7 you need to score 7+ on 1D10. If you are on Defender Base level 2 then 1 is deducted from the required score (7-1=6). Also hitting massed Aliens at their Base level (level 8) deducts 0 - (-5) from the required score, depending on the number of Aliens. A roll of 1 is always a miss.
Aliens may bomb the Players during the Alien turn. Aliens roll 1-5 D10s during they turn. Each score of 10 (during the 1st wave) forces the Players to make Save rolls. To Save a roll of 9+ is required, but the number depends on the distance between the Player and the bombing Aliens. E.g. Bomb from Level 8 against a Player at level 2 deducts 6 from the required number (9-6=3). A roll of 1 always means a failed Save.
Aliens launch 3-9 Ship Attack Squadrons from their Base level. Attack Squadrons move in certain patterns.
Destroyed Attack Squadrons may leave behind Power-up markers, which provides the Player who catches it either bonus points or upgrades for his gun.
10 points = Hitting an Alien at the Alien Base line.
20 points = Hitting an Alien in an Attack Squadron.
100-500 points = Destroying the last ship of an Alien Attack Squadron.
Mystery points = Hitting the Alien Mothership
0-300 points = Catching a Power-up marker left behind by a destroyed Alien Attack Squadron.
Each X points reward the Player an extra life. The X is dependent on the original number of players: 1 = 2000 pts, 2 = 1500 pts and 3 = 1000 pts. The required score is determined at the beginning of the game and doesn't change during the game.
Picture 2. A game in progress. Some Alien Ships have been destroyed. Alien Mothership is moving at level 9 and an Alien Attack Squadron is doing an attack run at level 6. Players are deployed at the Defender Base levels 1 and 2. The small marker at the level 4 is a Power-up marker on its way down for any Player to catch it.