The game has held up well in its design, but it's obviously held back by the limitations of the Game Boy. This mainly comes up with the respawning enemies, who are eligible to respawn immediately after their spawn point comes back into view. This means that unless you kill an enemy with his spawn location in view, he will respawn right after being killed. Although it's annoying, it's a double-edged sword; respawning enemies make it more difficult to avoid getting hit, but it also makes it easier to farm health points when low on health - there was one spot where I made an enemy respawn infinitely by merely jumping to full height and landing back on the ground.

The respawning enemies will be the thing that holds this game back, but the game underneath that inconvenience is actually really good. It's ahead of its time, being one of the earliest examples of a Metroidvania. The difficulty picks up quick, but the game has unlimited continues if you write down the passwords. The Pizzas scattered about the map give you an extra health bar if you die, and the game is pretty liberal about them. The turtles' powers are great, but only Michelangelo's and Donatello's are worth playing with unless needed; Leonardo's is practically worthless except in specific areas, and Raphael's is too situational.

Combat in the game is very simple. Regular enemies go down in 1-3 hits depending on their size and type. Bosses, on the other hand, have giant health bars which drain one point at a time. The Bosses have predictable patterns, but the fights are still difficult. And of course, there's the final boss, which consists of beating all 4 game bosses sequentially and is followed by a showdown with Shredder himself.

Personally, I love the game. I wouldn't say I recommend it to someone who is completely unfamiliar with the Gameboy, though - the respawning enemies and limited moveset might get in the way of the fun for some people. But I would still recommend it to fans of action adventure platformers and Metroidvania games. And of course, for me, it's another story altogether. This was one of my favorite games as child, so I'm absolutely thrilled playing it.