This game is awesome. It is free and it is very easy to pick up and learn. It's inspired by early coin op platform era games, and it rolls a ton of influences together in a deft manner the way Shovel Knight does.
Unlike so many of those games, this game plays buttery smooth and has fantastic control. Oftentimes those black box NES titles aren't quite as accessible as we recall them to be, but this one is.
The game is by no means easy. Its very hard and challenging. The special sauce in this game is the way scoring works and the nature of each level. You have completely different play-styles depending on how bad you want to get a high score. And each level has not only a different theme and structure/layout, but very different enemies and other elements that really keep you on your toes. In my first 5 minutes I thought it was just a cute game. then after 10 i figured out the scoring system. 20 minutes i beat the second level (which i wasn't sure if i could do) 30 minute i got a perfect score on the first map, and died in the absolutely insane level 3. (I'm currently able to get about halfway through level 3... but its a busy place.)

Darkula is not a perfect game. It's biggest flaws is probably the fact it doesn't save high scores. its also annoying that it cannot be alt tabbed conveniently.

Other than it, its perfect...Play this game!