very nice game!
it kept me occupied through the whole game! the extra mission was fun! extra seven is a nice boss! i beat it on normal with a tiny bit of health left! though there are some things i would like to suggest for PI4:
BALANCE THE SIHPS! the keyboard is just too slow to dodge the freakin loads of bullets sometimes thrown towards my head! i played through the whole game with FX, not bothering to try with ether... (i tried it in the tutorial and she was slow like hell compared to FX) not bothering to try with ether as well because her weapon was only a tiny bit wider, while i didnt need that... if her weapon would be stronger as well it would be better! and maybe let FX not directly follow the mouse, but let it have some delay and then he accelerates after the mouse... now its very easy to dodge stuff...
upgrades to the ships: now the ships start with and have through the whole game low damage weapons INSANE fire rate and they are very fast, but that should just be improved after each stage, at the cost of score (player can decide to buy upgrades and which (like overall weapon power, overall weapon fire rate, ship speed, ship health))
other upgrades like regeneration and different weapons would make the game better as well... like weapons have a certain upgrade limit, and then you have to buy a new weapon (or you can buy that weapon before you have fully upgraded). special one-time use weapons would be cool as well, or an upgrade where you can temporarily shift into another dimension when you want with a remaining energy level so people have to gather new energy first by destroying stuff before they can shift again.
enemies have more differing weapons: now all enemies except for bosses are using round slow bullets. this is very boring, even though nearly every ship fires it in a unique direction. it would be more fun if there were also regular enemies with lasers or that blue pulse gun (it rocked)! maybe some homing missile would be cool as well, and you can dodge them by letting it race past you because they can't steer well (when they fly past you they will leave the screen and not come back)
turnable ships: it would add an extra dimension if you could also turn the ship, you could for example hit enemies coming from backwards or from the top of the screen, and there are more boss attack possibilities!
I would like to wish you success on Project Inthri 4, and would be glad if my suggestions would be noted ^^ thanks for reading!