5 perceptual skills for drawing:
The perception of edges.
The perception of spaces
The perception of relationships
The perception of lights and shadows
The perception of the whole, or gestalt
h10.
h11.
h12. ---------------------
| 1 | 2 | 3 | 4 |
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| 5 | 6 | 7 | 8 |
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| 9 | 10 | 11 | 12 |
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| 13 | 14 | 15 | |
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These numbered squared represent sliding blocks which can only move
into the blank square.
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| 1 | 2 | 3 | 4 |
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| 5 | 6 | 7 | 8 |
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| 9 | 10 | 11 | 12 |
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| 13 | 15 | 14 | |
---------------------The puzzle inventor Sam Loyd applied for a U.S. patent for the above puzzle (the one with the 14, 15 swapped) but since it could not be "solved" - i.e., put in the correct order 1, 2, ..., 15 - no working model could be supplied, so his patent was denied.
We can do anything we like, we can sweat tears, we can stop and start again: but when we are in a wrong position, nothing will help.