Infinos Gaiden (外伝) - Hard 1CC (EX) [462k]

The EX Stage can only be accessed after you beat the main path, then once you beat Stage 6 Boss, the core will linger around, so fly into it to enter the EX Stage. If you wait, it will then disappear and you'll go into Stage 7.
EX Stage references the previous Infinos games and Picorinne Soft said they want to remake those, but when that will happen is up in the air.
You only get powerups at the start of it, not during it. It might be possible to beat the stage with Red or Green weapon, but when enemies come from all directions, it's better to stick with Blue.
Buy the game here:
store.steampowered.com/app/77...