The phrase "level gimmicks" refers to unique or unusual features or tricks within a specific level or stage of a game or activity. These gimmicks are designed to make the level more interesting, challenging, or fun for the players. Full definition
There are instances where players will randomly find hidden blocks containing stars or myriads of coins, and many level gimmicks will often screw players over. (wizarddojo.com)
Hopefully those videos should get people even more interested in buying New Super Mario Bros 2, or less skeptical about the game if they're too stubborn to even consider it, since Nintendo seem to be amping the difficulty up and adding all kinds of interesting new level gimmicks in this title! (gamingreinvented.com)
The levels are memorable and stand as some of the best examples of how to design an environment for gameplay in recent memory, while the core gameplay is as satisfying and fun as it ever was, improved by the addition of some cool new powers and level gimmicks. (wolfsgamingblog.com)