The atmosphere is fantastic. Gray scale perfectly give vibes of abandoned city. Player runs absurdly fast and has unrealistic jumping force, but that's actually fun in this game.
There is one thing I don't like in this. It is a level design of cave stage. This level is way too dark, even if it's forgotten city's cave. My eyes had hard time finding next platforms. Also these platforms are not visible in player's range, so it's rather guessing time to perfectly land on them, stop, and jump on next one. Also the broken ladder is misleading. For 10 minutes I was trying to find path beyond cave's jam just to discover you have to get out of the the same way to entered. I felt disappointed that I wasted time there.
To sum up, that's fun game with very smooth jumping mechanics and a bit too fast player running speed. Except cave level, I enjoyed exploring this forgotten city. Good entry!