Ovenbreak will forever be a masterpiece in terms of time killer games. It has everything you need: a multitude of cookies to obtain for free, obtainable costumes (which aren't necessary for story progression), decent OST, highly rewarding events, weekly game modes which also reward you with in-game currency, and no annoying pop-up ads. Props to the devs for amazing coordination because the only difference between a normal player and a paying player is the amount of time spent on the game!