2 Saved 9 bytes thanks to Wheat Wizard!
source | link

PowerShell, 2020 11 bytes

### ###4#
1#24#31#3
## ####2#

Abuses comments (#) like crazy, and the fact that a single number placed onto the pipeline gets output as-is. The above prints 1. Try it online!Try it online!


#1#
###
 2#
#4 
###
#3#

Rotated 90 degrees clockwiseFrom here, this now prints 2. Try it online!


### ##
3#42#1
## ###

Rotated clockwise againyou can easily see that each rotation yields only one number that's on the "left" of the comments, this now prints 3and so there's only one number that will be output per rotation. Try it online!


#3#
###
 4#
#2 
###
#1#

Final rotation, this prints 4. Try it online!Saved 9 bytes thanks to Wheat Wizard!

PowerShell, 20 bytes

### ##
1#24#3
## ###

Abuses comments (#) like crazy, and the fact that a single number placed onto the pipeline gets output as-is. The above prints 1. Try it online!


#1#
###
 2#
#4 
###
#3#

Rotated 90 degrees clockwise, this now prints 2. Try it online!


### ##
3#42#1
## ###

Rotated clockwise again, this now prints 3. Try it online!


#3#
###
 4#
#2 
###
#1#

Final rotation, this prints 4. Try it online!

PowerShell, 20 11 bytes

#4#
1#3
#2#

Abuses comments (#) like crazy, and the fact that a single number placed onto the pipeline gets output as-is. The above prints 1. Try it online!

From here, you can easily see that each rotation yields only one number that's on the "left" of the comments, and so there's only one number that will be output per rotation.

Saved 9 bytes thanks to Wheat Wizard!

1
source | link

PowerShell, 20 bytes

### ##
1#24#3
## ###

Abuses comments (#) like crazy, and the fact that a single number placed onto the pipeline gets output as-is. The above prints 1. Try it online!


#1#
###
 2#
#4 
###
#3#

Rotated 90 degrees clockwise, this now prints 2. Try it online!


### ##
3#42#1
## ###

Rotated clockwise again, this now prints 3. Try it online!


#3#
###
 4#
#2 
###
#1#

Final rotation, this prints 4. Try it online!