Evolution system:

The biggest characteristic of the game is the evolution of the player's ship. The ship starts out in a form called BEAS, and evolves when the player collects EVOL capsules, which appear when certain enemies are killed. The player's ship grows in size and strength as it evolves, but certain forms may be difficult to use effectively, so the player must pace the evolution properly in order to succeed. There are 19 different evolutionary forms in total.

The ship's attacks that target airborne enemies gradually increase in strength as the ship evolves, but the attacks against enemies on the ground cannot be improved in the same way. Hitting the airborne Nyoiarei and Zanz? enemies with a certain amount of shots causes them to get knocked out, and the player's ship can dock into these enemies for a short period of time while they are knocked out. The ship's attacks against enemies on the ground increase in strength during this period. However, some ground enemies cannot be killed during this power-up. No further power-ups exist for attacks against enemies on the ground. The giant version of Zanz? cannot be knocked out, so the player cannot use it to improve their ground attack.

Devolution:

Players must collect EVOL capsules frequently in order to advance to the strongest evolutionary forms. Failing to collect a capsules during a certain period of time causes the ship to gradually "devolve" one level at a time. However, the devolution timer is stopped while the ship is docked with an enemy character as explained above.

The player's ship devolves into the weakest form, PISTER (one rank below BEAS), if it is hit by an enemy attack (this does not apply if the ship is in the BLACK DEAME or SUPPURATE forms). The farther up the ship is on the evolutionary chain when it gets hit, the longer the animation is for the ship to devolve. Though coming into contact with any of the enemies normally results in an instant loss, the ship is invincible while the devolution animation lasts, and the player may kill enemies by ramming into them. The player loses their ship only if they are hit by an enemy attack while they are in the weakest evolutionary form (PISTER), or if they crash into an enemy while the ship is not devolving.

Mutation:

Several evolutionary forms cannot be achieved just by gathering capsules. Mutation occurs if the player is hit by an enemy attack while in a certain evolutionary stage (or if they devolve over time from a certain evolutionary stage), and the ship's attacks become highly stylized and powerful if used effectively.
Reverse evolution

Reverse evolution is another special form that occurs if the player is hit by an enemy attack after a specific set of normal evolutions. The reverse evolutionary form, BLACK DEAME, is bat-like, and bears a completely different appearance from any of the other forms. The ship is unaffected by enemy attacks, and packs an extraordinary amount of firepower as it shoots numerous smaller versions of itself as its main attack. However, if the player fails to collect an EVOL capsule during the allotted period of time, the ship immediately devolves into the weakest form, making the transformation a double-edged sword. It is impossible to maintain the BLACK DEAME form throughout the game by docking with enemies, since its attack power is so powerful that enemies die instantly rather than being knocked out.

* General sequence :
1) When you are not invincible -> (get hit by a bullet) -> PISTER
2) All states -> (fixed time without collecting power-up) -> degenerate
3) PISTER -> (get hit by a bullet) -> die
4) All states -> (get hit by an enemy) -> die

* Evolution sequence (when you collect a power-up) :
PISTER -> BEAS (your starting level) -> BASUM -> SHARRU -> MISEAVE -> TWIPET -> DODOK -> ZUGAU -> KUES -> SHASUEM -> ZUGOGA -> GYASHARRU

* Degeneration sequence (at fixed time without collecting power-up) :
1) GYASHARRU -> ZUGOGA -> SHASUEM -> KUES -> ZUGAU -> DODOK -> TWIPET -> MISEAVE -> SHARRU -> BASUM -> BEAS
2) LAYSPER -> BASUM
3) SUPPURATE -> PISTER
4) BLACK DEAME -> PISTER
5) DEAME -> SEAS -> MALTO -> MEASA -> ZUGAU

* Mutation sequence :
1) All states -> (hit the orange smoke released by the 'bird' alien that flies from the screen bottom) -> SUPPURATE (bullet invincible)
2) SHARRU -> (degeneration) -> BASUM -> (collect power-up) -> LAYSPER (you front shot is invisible)
3) KUES -> (degeneration) -> ZUGAU -> (collect power-up) -> MEASA -> MALTO -> SEAS -> DEAME

* Opposite evolution :
DEAME -> (get hit by a bullet) -> BLACK DEAME (bullet invincible)

* Bomb upgrade :
1) Shoot horizontal stick aliens the right number of times and they will drift slowly down the screen. Dock with this to get extra firepower. This also works with the aliens that have extendible poles that spring out from their sides : just shoot them until they flash and dock with them.
2) You can also dock with the rectangular aliens (after you have shot them a few times). These appear close to the start of the game. It seems anything you shoot that then drifts slowly down, you can dock with (which increases the bomb power).