.  1  .  .  .  .       .  1  .  .  .
 .  .  .  2  .  .       .  .  .  .  1
 .  .  .  .  .  3       .  .  2  .  .
 3  .  .  .  .  .       1  .  .  .  .
 .  .  2  .  .  .       .  .  .  1  .
 .  .  .  .  1  . 
         
   Symmetric on          Symmetric on
180-degree rotation   90-degree rotation

Figure 2: Examples of rotational symmetry in solutions.