It's been a while.
Bomb - Normal
Shepardus - 140,271,280 - 4 - Normal - v1.1a
Piercing - Easy
Shepardus - 95,374,810 - 5 - Normal - v1.1a
All my scores above are also v1.1a, not v1.1. Doesn't make much of a difference though, I think v1.1a is just minor bugfixes on top of v1.1. The update isn't on DLsite for some reason - the updater and the changelog are
here.
Edit:
Fixed - Easy
Shepardus - 131,326,300 - 5 - Normal - v1.1a
Bomb - Easy
Shepardus - 163,388,550 - 6 - Normal - v1.1a
By the way, fun tip: If you press V while hovering on top of a replay in the replay menu, it copies info about that replay to your clipboard, including all the info required for score submission here except stage and weapon. Very thoughtful of the dev.
Edit 2:
Circle - Extra
Shepardus - 357,362,500 - ALL - Mirror - v1.1a
Circle + Mirror is pretty silly: Circle reflects bullets while it's active, Mirror reflects bullets while it's not. As long as you never let go of the shot button and don't try to use the circle reflection with no energy (reflection doesn't work then) you can't be killed by bullets. In fact, the suicide bullets in Extra difficulty actually makes things easier because it gives you more to reflect with Mirror. Enemy collisions can still kill you, so that extra firepower helps. Also the circle doesn't seem to entirely work on homing bullets so I use mirror in those parts to be safe.
Even though the mode's trivial for survival, there is a bit of scoring you can do here. Collecting red crystals and medals increases the value of medals, but dying reduces those counts by a third. Red crystals also increase the value of bullet cancels. You can get big cancels by destroying a bunch of enemies to spawn their suicide bullets, and then activating circle and destroying an enemy to which you're anchored to cancel them all. Increasing rank increases the amount of blue or red crystals you get from destroying enemies, which lets you use the circle more (since more blue crystals = more energy), which is good for scoring since using circle lets you get more red crystals from enemies and also lets you cancel for red crystals. However, there aren't many safe places to increase rank since the way you do so is by keeping the circle active with no energy, which disables its reflective properties.
To establish a baseline I cleared the game once without using circle at all (except a little bit on the stage 2 boss, but that ended up hardly making a difference). Using only mirror I scored 146 million points, though that was marred by three deaths on stage 4 (wasn't prepared for swarms of enemies running into me...). With circle, I got the score posted above (357 million points), though that was with two deaths in stage 6 that probably lost me a significant amount of cashing in on high-value medals. I've seen two videos of Extra difficulty Mirror + Circle (which are also two of the three clears I've seen of Extra difficulty, the other being Bomb + Cannon), but this is higher-scoring than either of those (though not by much).
Edit 3:
Circle - Extra
Shepardus - 562,660,980 - ALL - Mirror - v1.1a
I found out that the maximum multiplier is 127.