Cyber Core (PC Engine)

Invincibility	        MIKARIN
Easy mode	        YANDI
Higher Difficulty Level	HIGEPIN
Arcade mode	        MAKIRIN

YANDI - Easy mode seems to give you more enemy drops: lives, shield power, smart bombs, and invincibility.

Stage 4 Boss - is easily defeated by bombing the middle ant guy before shooting the rotating worms.

Stage 5 Boss - The mother brain has a fixed movement pattern where it at one point does a few snaky movements and then goes right, all the way down and across. Make sure to avoid this.

Stage 7 Boss - Be sure to avoid the yellow shots and the green homing projectiles from the boss itself. The rest can be shot. The green projectiles can generally be avoided by dodging to the side and upwards, making them fly offscreen.

Secret Super-Weapon Pick up weapons: Red, Blue, Green, Green, Yellow, Red. Get hit and lose the weapon mutation.

I think this game is generally underestimated, I think it controls incredibly well and has an interesting weapon system. The levels are well designed and varied - each level has a completely new set of enemies, and they are placed together in ways where their abilities synergize to create unique challenges (e.g. Stage 7 where large enemies are forcing you to move horizontally, while vertical cannons are boxing you into a smaller space. The bosses have unique challenges, sometimes in a puzzly way (e.g. the Stage 5 boss where you easily defeat the boss by focusing on the ant and not the weird worms circling around it).

Clayton Walnum, Video Games & Computer Entertainment, January 1990:

As for playability, this is one tough game, a bug blastathon that will leave your controller hand aching. As with many shoot-'em-ups, until you learn the enemies' attack patterns, even the first level will seem to require superhuman coordination and speed. You'll definitely want to have your turbo fire cranked up for this one. [..] In summary, Cyber Core is a fast-action shoot-'em-up that's challenging enough to tax even veteran gun hands.