Kid Adventure is a throwback to the retro worlds of Capcom, Sega, and Nintendo. The entire presentation of this hack limits its colors to resemble the 8-bit graphical era of SNES and Game Gear. It does an almost perfect job of it except the fact that the background's alternate scrolling rate gives away that there is more than just the sprite layer and one object layer. The level design is also simple, yet the levels are longer than most hacks' levels. It starts weak but gains steam and utilizes a variety of resources, in often clever ways, to make each level unique and the harassing aspects difficult to conquer.
Kid resembles a Sega-ified Pac Man with Sonic-style shoes and a backwards hat, while Myfy is a blue Kirby with a propellor on his head and that big smirk you see on Sega characters. Myfy hovers over Kid on the overworld. When Kid has 1HP left, he switches places with the smaller Myfy but it's done in such a manner like Mario's transformation from big to small, and Myfy has no gameplay differences from Kid other than that. To me, that's disappointing, yet at the same time, this method of implementation would have to force you to take damage in order to take advantage of Myfy's mechanics. It's a cute but moot feature.
There's a level design aspect that contradicts the dialogue of the character right before the space, which claims only Myfy can get through the area you need to fly in. By duck-jumping, Kid can make it through as well. One other level design choice I didn't like was the fact that a canon path involved falling through toxic waste, and all other toxic waste prior to that was lethal. It's very deceptive to the player, who might assume he's gotten himself stuck in a place he's forced to die at the end of that big maze in the laboratory.
Make no mistake of it: while this hack starts easy and begins to creep up in the midst of Palmtree Beach, Ketchup Volcano is a ball-crusher from the moment you grab the P-wing. The high difficulty continues through the final level, and the first two bosses of that stage feel like the calm in the eye of the storm before a boss that's a puzzle to figure out.
The message boxes picked up some issues when it was translated from French to English: several of them have an extra space, causing a chunk of dialogue to get cut out.
*** FINAL BOSS SPOILERS ***
If you're absolutely stuck on the final boss, there is a hint in the dialogue in the room before the lab tanks which tells you about an invisible ladder prototype in Biza's room. You can't enter the pipe without beating Biza, but don't you remember that kind of wall from earlier when you fell through the toxic sludge into that area with the stars?