Interesting mechanic! I like the constraint it places on mouse movement, and the game gets nicely frantic. It did often feel, once I got sufficiently long, that it became near-impossible to lose that length without hitting the edge - and, sometimes I got forced into that situation if more slimes happened to be spawning on the side the mace was not on. My best was 508, which is probably not a very high score, but I found it to be a pretty difficult game!