Do you long for the fun of those 8-bit exploration games? Do you want to relive, platform jumping, weapon collecting, and highly pixelated art? I give you Doukutsu! Also known as Cave Story to use a literal translation of the name. It's a modern game but it was built to be as close to 8-bit classics like Metroid and Milton's Secret castle as possible.
Just look at those lovingly crafted, square edged graphics. Even the sound and music play like those limited channel, simplified beeps that marked the era. The game plays very smoothly even with just a keyboard but if you use a game pad then it feels even more like those classic titles.
In Doukutsu you play a guy who wakes up in a cave and saying more than that would spoil things. Besides, that's all of the information you have to start the game with and what would be the fun in an exploration game if someone hands you the info. You'll proceed to explore the cave, shoot up monsters, fight giant bosses, solve platforming based puzzles, and search for the power ups that will give you access to the next area.
Besides being a blast of complete nostalgia Doukutsu is a lot of fun. It's challenging but not so challenging that it made me frustrated. You'll encounter a tough boss fight about ever ten minutes of play which means you'll encounter a lot of variety in enemies as you get through the game. The environments are particularly large which means you'll spend quite a bit of your time player trying to find your way through them. There are plenty of bonuses hidden in the game to reward the deeper exploration, too.
The biggest problem with the game is that it is just too short. For most games that are too short it's a problem of not getting your value worth (see Heavenly Sword's 3 hours of actual gameplay for $60 for a recent example), but in Doukutsu's case I was just left wanting a lot more. A person who still has their late-80's skills will probably be able to finish it with under six hours of play. The areas may be huge but there's only about six major levels (depending how you count things) and are very linear.
There is one more issue with Doukutsu and that is the game text was originally in Japanese. There is a patch to translate the game to English that if you do not read Japanese you will want to install before you play the game. Sadly the dedication to duplicate that 8-bit gaming was not replicated by the translation team; the conversations are coherent and not filled with Engrish. Would it have killed them to tell me, "A winner is you!"?
Doukutsu may be short but it's entertaining for every bit of that game and digging into the cave is fun. The whole thing is like being transported back to 1987. It's well worth the price tag and your time.