If you've played Out of This World or the Abe series, you will love this game. Heart of Darkness takes place from a 2D view and is in some ways like a platformer, but more emphasis is placed on figuring out how to progress than reflex heavy action. You will need to be quick for some areas, but fast reflexes alone will never save you. You must analyze your situation and figure out how to progress, often taking advantage of your environment to do so. This is where my synopsis comes in. Describing this type of game is hard, but if you play HoD or have played the other games I mentioned, you will immediately see the difference between this genre and regular platformers.
Story Platformers usually have so little emphasis on story that I don't even give them a story rating. HoD's story pales in comparison to games like Final Fantasy or Metal Gear Solid, but it is very good for a platformer. The basic plot is, a boy named Andy had his dog stolen by a solar eclipse, so Andy jumps into his homemade rocket to go to another dimension and fight the shadows, along with helping friendly, flying creatures. The story is told through very well done FMV, with great animation and voice acting.
Graphics Amazing. Easily one of the best looking 2D games of all time. The graphics look like cinema worthy CG, and were probably a major factor in why the game took 5 years to develop. The backgrounds are vibrant and interactive, with detailed character animations. I got this game after owning a PS2 and GCN for months, and the graphics still amazed me. Good thing they're so good, you'll be seeing the same screen a lot...
Sound Amazing. The soundtrack is performed by an orchestra, and the voice acting is well done. The sound effects are very high quality.
Gameplay Ah, now to the love it or hate it part. The thing about this kind of game is, you die, a lot. Some people will find this tolerable, and keep trying until they solve the puzzle (like me), while some will curse the game and utterly despise it. If you have never played this type of game before, I would strongly recommend renting it to see if you can tolerate the difficulty. Your character, Andy, has a variety of moves. He can run, jump, summersault, climb, and for most of the game fire projectiles. Using the environments and your weapons creatively is what makes this game so fun. Unfortunately, the game is a little short, and due to its nature has terrible replay value. Various difficulty settings give the game some lastability though.
Conclusion This game is not for everyone, but if you like this type of game, you need to get Heart of Darkness due to the scarcity of its genre. The length is short, but the time you play is something special.