New slime block mechanic with snapshot.

[jxu]

Most everything I've built with pistons since they were introduced still functions as intended. And if you get good enough at usin' 'em, they can be just as fast as piston-less builds.

It's really the other way around: the challenge has always been to get pistonless builds to be as fast as piston builds (ex. CLE vs instacarry, xor gates). Pistons always have the advantage of instant block moving (the instant they move the block they're pushing/pulling becomes nonsolid)