The rewind mechanic is more complicated than that. It rewinds everything back 10 seconds or less depending on your score. So that includes doors , bullets , pickups , enemies position etc. It doesn't reload to the last check point, it takes you back in time. Please, try the game more and give it another chance as our programmer worked very hard to implement the feature.
I'm glad you enjoyed the art aspect of the game , I will check your game out as soon as I can. Thanks :D