ah the shovel's just, really good - the AoE damage makes it easy to wipe swarms of enemies quickly, swings deleting bullets makes later/higher-density enemy attacks far more survivable, and there's enough of a cooldown between swings that it's easy to trigger the coin autocollect while maintaining damage output
somehow i didn't register that the enemy spawn points were tied to points in the environment (despite recognizing that enemies always spawned in big groups at the top/bottom and in smaller groups around the edges) until i saw this/went back and looked at gameplay video i recorded, maybe adding animations for the doors opening would make that more obvious
overall the randomness is good in a lot of ways as-is i think (likely due to the grab-bag algorithm, i did feel that the time i spent with each weapon was fairly equal, and even with spawn points i started getting a semi-accurate sense for whether a big top/bottom wave or a room-perimeter wave was coming next, after a while); so likely all that's needed really is the additional visual telegraphing, to give the player a quarter-second heads-up on where they should be stepping away from