You Only Need Six

This is one of the new possible maps for Sokoban Level 3 in Hack'EM. It has 12 boulders and 10 holes, leaving 2 spare boulders.

  -----         --------- 0 boulder
  |...|         |.+.....| ^ hole
  |.|0|-----    |^|.....| > starting position/downstairs
---.0.--...---  |^|..<..| < upstairs
|...0....|...----^|.....| + door
|.....|0.000.>^^^.|.....|
|....||..|...---..|------
-------------- ----

Strategy

  -----         --------- E ll
  |...|         |.+.....| G dd
  |.|G|-----    |^|.....| F lddl
---.F.--...---  |^|..<..| G u
|...E....|...----^|.....| D ulll l
|.....|D.CBA.>^^^.|.....|
|....||..|...---..|------
-------------- ----

  -----         --------- B u
  |...|         |.+.....| A rrr
  |.|.|-----    |^|.....| C ll
---..G--...---  |^|..<..| B drrr rr
|.ED.....|...----^|.....| C ulll
|.F...|..CBA.>^^^.|.....| G u
|....||..|...---..|------
-------------- ----

  -----         --------- D d
  |...|         |.+.....| C rrrr drrr rrrr r
  |.|G|-----    |^|.....| E rrrr rrdr rrrr rrrr u
---...--...---  |^|..<..| F urrr rrrd rrrr rrrr ruu
|.EDC....|...----^|.....| D urrr rrdr rrrr rrrr uuu
|.F...|......>..^.|.....|
|....||..|...---..|------
-------------- ----