Hydra Glides

Have you ever see Hydralisks that move like a snake? What you will witness soon in this replay are a bunch of Hydralisks that glide and spit together in one same spot. This hack (or perhaps a bug) is known as the Hydra Stack by some community some times ago, but honestly, this is the first time I see it myself.
This bug was presented in the replay by someone called [M]ake7upURS (2041-1289-111) from US East Server. He is using the orange Zerg at 6. Some hints on how the Hydra Gliding works is with the burrow command thingy. Once the Hydra unburrowed from the ground and start moving to a certain spot, the Hydralisk's shadow "GONE". With its shadow gone, these Hydralisk can now started to glide and attack together in one same spot. Most bugs in Starcraft are always connected with the disappearance of unit's shadow.

With the gliding ability, the Zerg Hydralisks are like invisible (of course it you storm it with High Templar, everything gone). It gives advantage not only in attacking power, but also less chances of the same Hydra being hit.

I have uploaded the replay at:

http://www.megaupload.com/?d=5W7XEM9L

P:S This replay is a contribution of na3r0k (15-700-16) of US East.