Some reviewer at some video-sharing site describes this as one of the hardest games ever made. If you ask me, I do find it a little tricky. But I don't find the game that hard after playing it numerous times, and coming up with ways to get around the obstacles. I am writing this review because a few days ago, I played the game, got the best ending, and done so without using a single continue.
In the game, the player controls Dr. Jekyll whose goal is to walk through six places to reach the church where he would wed his lady. But if you think the journey would be smooth and peaceful, various obstacles and dangers await along the away which the doc must avoid. If Jekyll gets stressed too much, he will transform into the hideous Mr. Hyde who must destroy a number of beasts before being able to revert back to Jekyll. The game is mostly original, though Hyde's energy ball move appears to be inspired by Mario's fireball attack.
One complaint some gamers have about the game is that Jekyll walks rather slow which makes it challenging to dodge things like falling birds or bad musical notes. When getting struck a lot by those things, don't get frustrated. Instead you should be thankful, especially if getting stressed and taken to Hyde's world is a chance to restore your life gauge and removing some of the nuisances on screen.
Another complaint some gamers have is that Jekyll's cane does not do anything other than removing bees. Well, it is believed that Jekyll is designed to be a peace lover who should not attack anyone (a total opposite of his Hyde character). But to not make Jekyll completely defenseless, the designers made the cane usable against the insects.
What do I like about the game? The music fit the worlds of Jekyll and Hyde. The cat and dog really sound like a cat and dog. And best of all, the game has two endings which is rare for an NES game.