I really like this game. Got to wave 90 and had a ton of fun.
My favorite things about this were the excellent animation and sprite work. I love the look of the enemies and their movements and actions look fantastic.
I like the charge up of the weapons causing them to do more damage, and having to give that up to fire a large burst feels great. That said, it feels like the melee attack is very weak and I only ever relied on the beam attack to kill anything, and exclusively took beam upgrades when possible. Later in the game it becomes very important to have high move speed to avoid the swarms as they get larger, and to get a large swath of enemies in the beams as they fire. That said, it feels like there is a very clear optimal choice to take as many guns as possible, since none of the other upgrades even come close to providing as much benefit. Overall I like the upgrade system, but it might be more interesting if the tradeoff between melee and the beams firing was more meaningful.
I love the design of the big tombstone/boss enemy. The way it has an attack to match every other enemy type (except the small ghost) really makes it feel like it's tied into the world, and it feels like the design ideas behind dealing with each attack are solid. The beam always tracking clockwise does mean that the optimal strategy is to always run around the arena counterclockwise, but once you know that it does provide for interesting gameplay baiting it out and running along with it. It seems like the dotted line that shows the beam is about to shoot doesn't show up most of the time, and when it does it's so short it's not useful. This means you always have to track counterclockwise if the boss is able to attack. The scatter shot is probably too hard to dodge at low movement speed, but later on it becomes a more interesting challenge, at least when the boss even fires it in the player's direction. Most of the time this attack is fired away from the player. This is effectively the same as the boss doing nothing at all, and I'm not sure why it does this.
The scariest enemies are definitely the ones that fire the beam weapon. They are easy to deal with when grouped or in small amounts, but as soon as they are spread around in larger number it becomes a very interesting challenge to dodge all their beams at once. They synergize well into every other enemy type and really keep you on your toes. Due to the way enemies always spawn in the corners, they don't provide as much challenge until later on when you're forced to move before spawning completes, so it could be interesting to have them spawn around the map a bit more.
The candle enemies are the next most challenging. I like the acceleration and aim on their shots. It means you always have to pay attention to how the shots are behaving to know how to dodge them. The big ones especially with their 50 health damage and increased shot size were able to trap me if I wasn't paying attention.
The purple ghosts act a bit more like damaging terrain than enemies most of the time. I like that they seem to occasionally bounce away from each other to keep the movement interesting, but it didn't happen a lot and I think it's just a quirk of whatever is keeping them from clipping into each other. I think they might be more interesting if they spread out even more or had some more interesting movement patterns. As is, I don't think they feel different enough from the ghosts. Usually the round ends with several of these still alive and posing no threat at all because of how slow they are.
The white ghosts are basically the same as the purple ones, and don't pose any challenge on their own. The rounds with only white ghosts might as well be free wins. I do like that the game has lower difficulty rounds to mix up the challenge as the wave count increases, but after a while the only purpose of these rounds is to add breathing room to finish off one of the big boss tombstones. Most of what I said about the purple ghosts applies here in that I feel like giving either these or the purple ghosts something to distinguish each other would be good. Also, the big white ghost should probably be faster than the regular one, not slower. Making it slower just makes it more similar to the purple ones.
Overall, I really like this game. I think could use a little more polish if you had any desire to continue to work on it, but it is already great fun and I had a wonderful time playing it. Thanks for all the work you put into making this!