As a huge tower defense buff, I've really enjoyed the Sentry Knight series. I'm enjoying this rendition, too, but started to experience some significant hitches during the gameplay. Every five to ten seconds the game will freeze up for about a one to two seconds. This didn't happen at the outset, but only began occurring after I engaged in some level grinding between the first two stages. I have a decent rig, so my hardware shouldn't be the source of the problem.