Do you mean the black screen that happens before the boss? That's due to rendering a frame including all shaders (while the screen is fully black to hide this) to prevent stutters when she does each attack for the first time. I forgot to make the object responsible for pre-loading the shaders queue_free() after the fade in starts, so there is some additional lag on lower-end devices for 4 seconds (that's how long each effect is active for). I'll fix this in the post jam version. Thank you for playing!
Huh, I've never noticed it during testing, would changing loading the scenes (the individual attacks are scenes) from load() to preload() fix it? I'll upload the updated version (fixes lots of bugs players have found) after the jam voting period ends as well as the project files. Otherwise, do you have any tips to avoid preinstancing stutters?