Stealth game
Also said as Stealth action
You avoid being seen rather than fighting. Guards have vision and hearing that you learn and exploit. It promises the tension of being one mistake away, and the satisfaction of never being noticed at all.
Stealth only works when the player can read what guards know. If you cannot tell why you were spotted, it stops being a skill and becomes a coin toss.
Say it
“Show each guard's vision cone, and fill a detection meter over one second rather than failing instantly. If you get spotted, the guard checks the last place they saw you, then goes back.”
Where you’ve seen it
Metal Gear (1987) made avoiding guards the point, and Thief: The Dark Project (1998) added light and sound. Mark of the Ninja (2012), being in 2D, draws vision cones and noise rings right on the screen, so you always know what the guards know.
Not to be confused with hiding
Lots of games let you hide for a moment. A stealth game makes avoiding detection the main verb, with guards built around it.