AlienCruise

Story-related; cannot be missed.

This planet is the little blue one in the upper right corner. The first level is pretty long and can be a bit hectic. Prioritize the UFOs since their lasers split and can make dodging difficult. There are two sort of minibosses, but both are short with simple attacks. The second level has the same enemies but more obstacles to avoid. The miniboss in the middle of the level is an eye mech. Just sit right next to it and shoot it until it is destroyed. The rest of the level is just obstacles and enemies. The third level is also pretty simple, with more obstacles and the same enemies. At the end, you'll go through a fast area. Stay in the center of the screen so you aren't blindsided by UFOs that fly in from the left.

The boss at the end of this planet is a nightmare, and in my opinion the hardest boss in the game by far (and the majority of the reason for the difficulty rating for this game). The first phase is pretty simple. Continuously fire at him while avoiding his three attacks. Stay in the lower left corner and he won't be able to hit you when he slams his arm on the ground. When the light balls come out, wait until they stay coming at you and slowly move directly up to the top, then to the right, and then around back down. Be careful to move slowly so you cover as little ground as possible, because he'll then immediately shoot up and have fireballs rain down. Dodge them while shooting him. You'll want to be able to perfect this phase without losing a single heart, because the next phase is much more difficult, and you'll need all your lives.

The second phase has a ridiculous amount of health, so be prepared for a long fight. He has a ton of attacks and things get really chaotic when he starts using two and even three attacks at the same time. Focus entirely on dodging and let the damaging of the boss happen incidentally while you dodge. I have noticed that there are a few attacks, such as the splitting lasers, the rocks coming up from the ground, and the two fireballs attacks (the ones that rain straight down and the ones he shoots in arcs at you) can all be avoided entirely by going right up to his knee as close as you can. Focus fire and you'll be safe from those attacks there. Just be sure to back aware before his other attacks. You'll likely spend quite a while mastering this boss's attacks and patterns, and expect it to require patience and practice to finally beat him.