Well done on getting this over the line in 18 hours - very impressive! I like the concept a lot - it's a clever idea with lots of potential, and you executed it pretty well here.
The red dots on some of them read as gun laser sights at first - took me a while to realise they were meant to be eyes. I also wondered what the point of having such obvious aliens (glowing skin and red eyes) but came to realise it can be a good strategy to keep them alive and eliminate them later when you need to lower the invasion meter.
I found very few aliens via the flashing light or freezing - possibly too subtle with so many people on screen at once. There were usually several in the light when it went off (though it was then fun to see if I could catch who was running away), while the humans are stopping and starting all the time so not easy to see who's freezing and who's simply stopping.
Weird shadows and off-colour skin were the sweet spots - not too obvious and not too difficult. Could be more fun to just work with that sort of thing... subtle visual differences that are easy to miss when you're not looking for them, but super clear when you are.