Extra lives:
-At 10,000 points
-At 50,000 points
-Every additional 50,000 points.
-Extra lives stop at 2,000,000 points.
Tips:
-You still get points of an enemy collides with mines or asteroids.
-Mine explosions persist for half a second, and they're pretty large. Don't fly into one after shooting!
-When you begin a level, try and get to the outside. You don't want to be between several bases.
-Asteroids have smaller hitboxes than mines.
-Levels wrap like in Defender or the "secret passage" in Pac-Man. Enemies will chase you down this way.
-Enemies keep coming. You could max out your score on level 1...if you wanted.
Game info:
Bosconian has a fairly complex set of rules for a shooter. The object of is to score points (of course) by destroying rocks, space mines, three types of enemy fighters, and enemy space stations. When all the stations are destroyed, you'll advance to the next level.
If you manage to beat level 255, the game rolls over to 0. The "Abnormal behavior" shouldn't prevent you from playing.
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I-Type fighter - tries to smash into you. Turns slowly.

P-type - Tries to swing around from the side

E-type - Fired straight from a station's core. Very fast. Can't turn unless in formation.

Spy ship - If this shows up and you let it escape, the enemy will be alerted to your presence. During Red Alert, tons of enemies will chase you.
Sometimes the fighters will attack in formations of five. Destroy the purple leader and his subordinates will flee. Destroy a whole formation for big points!
The space stations consist of six orbs and a bright red core. They are destroyed when you shoot the core
or when you shoot all six of the orbs. The core can shoot at you. After level 1, the core is covered with a shield that periodically opens and closes.
- Score table:
Asteroid 10
Cosmo Mine 20
I-Type (Leader) 50 (100)
P-Type (Leader) 60 (120)
E-Type (Leader) 70 (140)
Spy Ships 200, 400, or 800
Enemy Base Orb 200
Enemy Base 1500
Complete Enemy Formation 500 (I), 1000 (P), or 1500(E)
Thanks to StrategyWiki for the images and score table.