9
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16 steps. Can you do it?

The picture above shows two arrangements of four rectangular blocks, each labelled A to D. The arrangement on the left is the starting arrangement, the one on the right is the goal position. To solve this puzzle you need to slide the blocks around so that the starting arrangement is transformed into the goal arrangement.

Oh, but there's a catch...

You need to solve the puzzle in 16 moves or under.

A move consists of moving a block to a new position so long as you don't hop a block over another block, twist a block around on the spot, move a block on top of another block, or move a block out of the frame.

Good luck!

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3
  • 1
    $\begingroup$ I can do it in one move: rotate the puzzle 180 degrees. (Of course that's cheating.) $\endgroup$
    – MackTuesday
    Commented Sep 19, 2021 at 23:17
  • $\begingroup$ @MackTuesday Well done! $\endgroup$
    – End Antisemitic Hate
    Commented Sep 20, 2021 at 2:53
  • 1
    $\begingroup$ Is it allowed to push a piece by moving another piece and does this count as 1 move or 2? $\endgroup$
    – Vilx-
    Commented Sep 20, 2021 at 10:17

2 Answers 2

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14
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I think this works:

. B . .  0
. B C C
A A D .
. . D .

. B . .  1
. B C C
. . D .
A A D .

. . . .  2
. B C C
. B D .
A A D .

C C . .  3
. B . .
. B D .
A A D .

C C . D  4
. B . D
. B . .
A A . .

C C . D  5
. . . D
. . . B
A A . B

C C . .  6
. . . .
. . D B
A A D B

C C A A  7
. . . .
. . D B
. . D B

. . A A  8
. . . .
. . D B
C C D B

. D A A  9
. D . .
. . . B
C C . B

. D A A  10
. D . .
C C . B
. . . B

. D . .  11
. D A A
C C . B
. . . B

. D . .  12
. D A A
C C B .
. . B .

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1
  • $\begingroup$ I was happy when I just managed to get it in 16 :P $\endgroup$
    – Beastly Gerbil
    Commented Sep 18, 2021 at 15:11
11
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Took me some time, but I got 13 steps:

Screenshot of each step in an HTML grid.

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5
  • 5
    $\begingroup$ I guess you can combine the two consecutive orange steps 3 and 4 to save a step. $\endgroup$
    – RobPratt
    Commented Sep 18, 2021 at 16:52
  • $\begingroup$ This is 12 moves, not 13, right? $\endgroup$
    – AAM111
    Commented Sep 19, 2021 at 18:23
  • $\begingroup$ @OldBunny2800 13, originally thought it was 14 for the same reason. $\endgroup$
    – Taco
    Commented Sep 19, 2021 at 18:54
  • 2
    $\begingroup$ I count 12 - moves 3 and 4 are actually just one move. $\endgroup$
    – AAM111
    Commented Sep 19, 2021 at 19:02
  • $\begingroup$ Ohhhh good eye lol 😂 $\endgroup$
    – Taco
    Commented Sep 19, 2021 at 19:13

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