This analysis by Robert Yang hits so much of what makes Invisible, Inc. a great stealth game.
You can always lose more. Unlike every other stealth game, slow and patient observation usually means slowly suffocating death here.
Incapacitating many guards the first time is easy; but they wake up again! You have to carefully time using your stun guns because they recharge slowly over several turns. Likewise, taking enemies out for good is hard and expensive, because you may never again get more ammo for that gun (if you even have something that’s effective against their armor).
Because guards are rarely actually out of the game, every turn puts you in more danger of being overwhelmed, caught without the resources to get to your goal. It’s a constant struggle between pushing just a bit further and getting in way, way over your head.
Robert’s description of a perfectly-laid out plan foiled by one tiny unexpected detail is basically the game in a nutshell: Flashes of “I’m brilliant!” colliding with “OH NO!” and it’s a great, great time.