I was quite excited for this entry, because hey I made a stealth game too! So I was intrigued to see others try the concept.
The main gameplay mechanic is brilliant. It really fits well with the theme of thinking outside of the box. There were a few times I was like "what do I do?" but then I remember the main mechanic and I feel cool for utilizing it. The addition of the scroll wheel to help adjust the field of view is a nice touch too. The level design was very fun too, the concept of doing multiple tasks for a higher score is very good for this type of game.
A problem I had with the game was that it was hard to keep track of how the level was layout outside of the box, and I would have to guess at where the boundaries are/gonna be. I think if the outlines of the level were still visible when freezing the borders, it would make it a lot easier to plan out where to go next. I also had a frustrating time with the 3rd level, due to the way the guards are too far off screen and seem to notice you a little bit beyond their cone of vision. In general, I rather just go to a game over state right away when being spotted, because all I can think of to escape is to run around to find an exit. The main mechanic of stopping to freeze the border requires the player to stop and think, and it's pretty hard to do that when on the run.
Also, I think that marking all the guards should have just made an exit appear instead, because I wanted to get the lore bits, but I end up having to choose between finding the guards or the lore bits. I had a moment where I marked all the guards, but didnt realize I marked the last guard and was booted out of the level, and I really wanted to find that intel folder!
Overall though, the game controlled great and was very fun to play through, I'd love to see more expanded upon with this concept, because as it stands its a really fun stealth game! I def have a lot to say about it because I love stealth games like this ahah but I hope you dont think I dislike it, I love it lots! If you expand upon it more, I'll be happy to see it.