In this video I explain how natural mob spawning have changed in 1.9, and its effects on all sorts of farms based on natural mob spawning. I also explain the implications of entity collisions bug, that I found, and how it can be used to create a perfect witch farm. In a perfect witch farm all the spawn attempts that happend in it have 100 chance of success. I am also explaining how to design such a farm, showing as an example, a skeleton farm, which while not the fastest, is ually still optimal (especially for a single witch farm settings where there is no need to worry about the mob cap).\rbr\rbrModdeda aspects of the game (in MCP 9.18 (MC1.8.8) and MCP 9.24(MC1.9.0), used when appropriate):\rbr - chilled monsters (demonstration purposes only)\rbr - cranked up spawning (2000 ticks per second)\rbr - carpet mod (mob spawn debug information)\rbr - collision bug fix for 1.9 ! (hint)\rbr\rbrReferences:\rbr\rbrSkeleton-powered witch farm: \rbr\rbrGalias sand on a fence trick: \rbrIlmangos sand on a fence bug explanation: \rbr\rbrSpire max farm extimation for 1.