Good but not excellent
I could finish the first stage in the second playtrough, it's really hard, but not impossible, maybe you should require less heros of the harder difficulties for the first stages. Also the nightvision is kinda useless because you can't search corners with it.
Yes you are right, at the first instant I didn't realize coz I knew where they were, I tried again and yes it is very hard, although not impossible, as you said. (in fact I think the second level is harder than the 3rd one :) )
Game might be fun to play, but it's just to hard to find all of those heroes, I trried a couple of times playing, but can't even pass first level. Than I just remembered some parts where those heroes are and started using special items, which drained timer so fast I couldn't even use those items properly. I would understand such hardness in later levels, but now it's just to annoying to play it.
By the way, night vision can't go to corners, so it makes it's a bit useless.
Thanks for your feedback.
The idea is not to find all of them the first time you play, there are only a few that are not easy to find (particularity the blue hero), there rest are very easy, so use the specials to find those hard ones and remember where they are for next go.
With the night vision is to easy to find them, that is the reason why it does not go to the corners. So again, start for the hedge of the screen and finish with the center.
At the end just find as many heroes as you can, and use the sniper to easily find the last ones.
However I´ll take your advise and I will make easier the first level for the next game of the series.