Bonk's first game is a solid one.
Story-wise, there isn't really much of a story. Bonk must save Moonland and it's brainwashed inhabitants from King Drool. It's not much, but most platformers back then didn't have much of a story anyways.
As for the game itself, it's a platformer. The main goal is to get Bonk to the end of the level. Bonk's main attack is his head which he uses to bonk his enemies. He can't jump on his enemies like Mario, but he can jump in the air and do a ground headbutt which makes up for this. Bonk can also spin through the air and hit enemies that way too.
Bonk starts out with three hearts, and when he gets hit, he loses part of a heart. When he loses all of his health he dies and picks up right where he left off. Thankfully there are fruits and vegetables throughout the game to replenish his health. There is also meat that Bonk can eat too. When he eats a small piece, he can freeze all enemies on the screen when he does a ground headbutt. When he eats a big piece of meat or two small pieces, he becomes invincible for a short period. The meat also acts as a shield, but it wears off over time or if Bonk gets hit by an enemy. Finally, there's extra lives and extra hearts that Bonk can collect.
There are many flowers in this game, and these flowers are used for various things depending on their color. Yellow ones are used as springs, red ones give out extra health, blue ones give out extra lives or a lot of extra health, while green ones give out extra hearts. Some of these flowers are fake though, and can hurt Bonk.
There are several worlds in the game and each world has one or more level. At the end of each world, Bonk must fight one of the brainwashed inhabitants of Moonland. Most of the bosses are pretty easy and have predictable patterns, but there's a couple that can be annoying.
The controls for this game are pretty good. Bonk controls a little differently than other platforming characters so it might take some getting used too, but it doesn't take too long to get the hang of them. One button jumps and the other bonks. The jump button is also used to climb waterfalls and ledges. Finally, pressing the bonk button while in the air allows Bonk to spin through the air which can be helpful in some parts of the game.
The graphics in this game are ok, but they're a bit dated. There's not much shading for the sprites and background objects so everything looks a bit flat. Other than that though, everything looks fine.
The music is good too. There's not much variety in terms of it, but other than that it gets the job done and sounds better than some of the other early Turbografx games.
The game's pretty easy, especially if Bonk accumulates a lot of extra lives which is easy to do. The last world is the hardest part of the game so it might take some time to get through that, but overall the game's not too hard.
The biggest negative aspect of this game is the ability to zoom through some levels using the spin ability. Thankfully the developers made it to where this isn't possible in the sequels. The minor negative aspects include the dated graphics and the short length of the game.
Overall, Bonk's Adventure is a good platformer for the Turbografx-16 and is recommended for anyone who is considering buying the console. It's also available on the Wii VC and PSN for $6 so it comes recommended if you have one of those consoles too.