Hi there!! I took a few notes while playing your fun little game:
Instead of having Enter be interact, try making it E instead. Currently, the player has to take their hand off of the mouse to hit the enter key, whereas with E you can just click it instantly with your left hand, like most 1st and 3rd person shooters.
The text boxes write out the letters really slowly, it's currently about 1 letter a second. It doesn't spell out the entire sentence you were meant to read either. It might be working properly on your end, maybe on slower or faster machines it works improperly?
I'd pull back the camera from the character, since they block a good portion of the screen and it seems cramped. The movement speed also feels really slow, doubling it could make it feel a lot better. The slow pacing makes the gunplay feel less exciting than it could be if the player (and the enemies too) were sped up.
The color of the heat bar isn't bright enough, so it doesn't pop out in the corner of my eye. Making it a bright red or have it change from a bright yellow to a bright red as it goes higher could help too.
Enemies and friendly soldiers can sometimes get stuck trying to pass each other, directly trying to run towards the other in place.
On the world map it says to use AWSD but only the arrow keys instead.
Pressing "quit" on the Game Over screen doesn't hide the Game Over screen but still shows the "you're sure to quit the mission?". Also, sometimes when you die the game over screen doesn't even show up, so the game softlocks unless you pause the game and quit to the homebase.