This is the last shoot-'em-up and the first 'non-endless' game by Toaplan. A special version of Batsugun existed, originally it was only for the AOU show (Arcade Operators Union, an arcade game show held in Japan every year) and not for sale. After the Toaplan bankruptcy, the board started to appear on the second hand market.
Heralded by some as the first "manic shooter", Batsugun involved employees who would go on to form and work at Cave and continue to work in this subgenre. Batsugun saw an evolution in the use of complex bullet and enemy patterns and player fire power and hit-box.
The scoring trick on the fourth boss (destroy the two giant laser cannons, let the tanks appearing from the hangars fill the ramps and become red, bomb for 59,630 points a tank) was one source of inspiration for Battle Garegga's gameplay. (arcade-history)
As is the standard with most arcade shooters, players control their ship with a joystick and two buttons. One button (Fire) shoots the main guns, and the other button (Bomb) releases a smart bomb that spreads huge energy balls all around the player's ship.
As enemies are destroyed, the player gains experience points that are separate from the score. For every 288 experience points gained, the main gun will 'level up', becoming much stronger. This is analogous to experience points and levelling up in role playing games. The weapon can only level up twice, so after it has achieved its maximum level, 288 experience points will grant the player an extra bomb.
Players can also grab "P" icons to increase the power of the current level gun. A maximum of five "P"s can be collected; getting more after this gives extra points instead.
Collecting "B" icons increases the number of bombs, to a maximum of 7. (Wikipedia)