Really great stuff, the gameplay and presentation are spot on. I would've liked it if the stages themselves were more challenging perhaps, my only deaths were at bosses even on the spicy secret difficulty level. Also I found the dash following the cursor rather than the direction of movement a bit inconvenient since its main use seems to be using the invincibility to pass through walls of bullets.
Also, a native Linux build would've been nice, I had a some framedrops on the hardest level playing in Firefox, but nothing major.