6.70 appears to be the final form of 6.60. It's basically 6.60 with a couple of minor refinements and bug fixes. (I've edited out most of the 6.70 features list that was a repeat of the 6.60 features.)
Version 6 OverviewSome speed optimizations from Version-7 applied for higher frame-rate. Fires can be put out by dropping flame-retardant on them.