Feels like an excellently-made hybrid of Ninja Gaiden and Castlevania. Your player character controls well, and rushing through the levels feels fun with how fast they move — though, I do wish you could control how high you jumped by holding Z for a shorter or longer period of time. The levels are well-designed, balancing tricky platforming with enemy-focused challenges and separating the challenging bits with parts where you can rush through and acquire spirits. I found level 2 to be the hardest, especially with its tengu boss, though the Kirnos in level 3 are certainly the toughest regular enemies in the game — and the boss of level 4 makes up for the level being slightly disappointing in difficulty. The background music for each level is good and fits the Game Boy aesthetic perfectly. Overall, a great entry with only a few minor flaws. If you extend it, make it more difficult, and release it as a full game, I'd be interested in buying it.