I played it through a wacom tablet and it worked pretty well! I didn't know how to use the upgrades, maybe I did something wrong, is there a difference between them? I just bought a lot of them and kept slicing away. As Panpukin, I experienced some degree of lag too for some reason, and the logs would destroy me after a while.
Really cool entry though, I like the samurai theme and the gameplay. The ability to scratch the main logo was a nice touch haha. Good job!