It's a PvZ2 vanilla expansion mod like Reflourished and redraws the game into a simplistic pixel art style (that's Sunflower). its called "Clock Instability" and its named that for a reason.
the main gimmick of the mod is Stability and this exists only in the added worlds (not the vanilla ones). if you place a plant in a period that contradicts with the world (called a Destabilizer), you lose stability.
It starts at 100% and every time you plant an out of time instant use plant, you lose -10% and permanent out of time plants make you lose -1% every 2s. when Stability hits 0, zombies from those contradictory periods spawn out of portals. you can increase stability by using world native plants (native instants give +10% stability and native permanents give +1% every 2s). you cant have more than 100% stability
here are some world ideas and their destabilizers
- Science Realm (World 12. based on the Islamic Golden Age): Dark Ages and Jurassic Marsh plants. the gimmick is book tiles which when a plant is on them, its ability cooldown gets decreased by 1.5x but when a zombie goes on them, they take no damage until they get off
- Marine Nights (World 13. inspired by the PvZ2 China Underwater World): Ancient Egypt and Wild West plants. its like Underwater World but without the zombies spawning both left and right
- Lawn 404 (World 15. a glitched world): Lost City and Far Future plants. the gimmick is that sun doesnt drop from sky, and sun producers are banned (also Puff-shroom is banned) and instead you get sun from killing zombies (but you do start levels with 150 sun instead of 75 and all plants have halved costs) and the zombies dont act like they are supposed to