The game is your basic side-scrolling affair, albeit a very slow-paced one. Mickey leisurely strolls through the game's 5 levels, jumping over chasms and taking out a moderate amount of baddies along the way. Considering the fact that you can complete the game in under an hour, it is quite possible that this slow-pace was purposely implemented in order to lengthen the amount of time taken to complete the adventure. Whatever the reason, the sluggish—and sometimes slippery—controls make for a fairly unentertaining experience.
Mickey has two means of attack: jumping on his enemies or throwing marbles/apples at them. Throwing projectiles works exactly like you would expect it to, however jumping on your foes is a bit strange and takes some getting used to. You have to press the jump button twice—once to leave the ground and once to lift Mickey's legs, allowing him to land on enemies without taking any damage. Also, if you hold down the jump button while landing on an enemy, Mickey will be launched unreasonably high into the air, which can also take some getting used to—especially with the game's floaty controls.
Luckily, there are a handful of inventive level designs that save the game from being a complete bore-fest. In one of the later levels, Mickey is able to swim through the contents of a cup of tea, dodging sugar cubes that do their best to get in the way. Later in the same level, Mickey travels into the mouth of a milk jug that leads him to a candyland-esque world with a river of milk flooding the bottom of the screen. These lush environments and creative level designs keep the game interesting throughout, but the game's slow-as-molasses-pace still weighs down heavily on the game's overall enjoyment level.
As you might expect from a Disney-themed game, the visuals are quite endearing and the soundtrack, for the most part, fits right in with each level's mood. However, the soundtrack—while both lighthearted and joyful—tends to run at a constant tempo, causing the songs to bleed together and become monotonous by the time you get halfway through the game. The visuals on the other hand, despite some lackluster enemy designs, are extremely colorful and well-detailed. The backgrounds have some nice textures and the character animations are incredibly smooth. These two areas are the game's strongest points, but—as every old-school gamer knows—a game's aesthetics don't mean a thing if the core gameplay isn't there to back them up.
While Castle of Illusion does posses a handful of charming qualities along with some fairly inventive level designs, these things simply aren't enough to save the game from mediocrity. The slow, drab gameplay is too much for the positive aspects of the game to overcome. I've seen quite a few favorable reviews that score this game in the 8-9 range which is almost unbelievable to me. Being able to play through this game for the first time some 20 years after it's initial release, I was able to see it for what it really is, rather than what it was all those years ago—which is exactly what we try our best to do here at TTG Reviews in the first place.
Overall Score: 5.3/10 (Avid Disney fans will surely enjoy the charming soundtrack and gorgeous graphics that bring Mickey's world to life, but the core gameplay holds this game back from being a necessary addition to your Genesis collection.)
Here is a pretty funny commercial for the game raving about how great it is because it's 16-bit, which is quite humorous because the vast majority of Disney-themed NES games are far superior to this one.