At first this seemed like the usual endless-runner, but smashing zombies is way more fun than collecting coins. And choosing what to upgrade adds a fun strategic element to it.

I chewed up a LOT of time playing this game some weeks ago, pushing through until I finished the core map. The physics and increasing destruction caused by your armored vehicles is a whole lot of fun. Definitely a time-waster, but plenty of mindless repetitive entertainment if you're keen to check out for stretches at a time. :)