Yeah, I had trouble nailing the movement. Thanks for your feedback. About difficulty, it gets extremely difficult ~100 point mark. I might change that as it takes some time to build up.
This is how the spawning mechanic works:
Every 12 seconds, the games spawns 1 + (score / 10) enemies. So when you have 100 points it spawns 11 enemies every 12 seconds. This sorta balances it out and prevents infinite scores. So even though you can block infinitely eventually you will get overrun. Even if you play perfectly, swinging your sword once when surrounded by 100 enemies will increase your dark magic bar by 5 * 100 which is enough to fill the dark magic bar 10 times instantly and deal 100% of your hp. It's supposed to be easy to start but gets harder the more points.
Thanks again!