I made a short and simple domino puzzle, where there are four domino tracks that can be knocked over in any permutation, and the goal is to knock over the final path that will take down the domino fortress. Only one permutation should be able to do so. Please note that when a domino hits two dominos that are perpendicular, then it is blocked, but a domino can knock over another domino over the top of the fallen dominoes, unless they are too far apart. This puzzle should be a simple, easy puzzle to solve. Here is a Powerpoint Shapes version:
Number the four starting dominoes at the bottom from left to right 1 to 4.
I think the solution is 2 4 1.
The last move is #1, as this is the only one that could activate the path to the fortress. However, the double-domino blockage needs to be removed first.
The path that removes the blockage leads back to only #4. However, tipping #4 first activates two paths that knock each other out, so the left of those two paths needs to be disabled first.
The path that causes that left one to be disabled leads back to #2 and #3. Tipping over #3 also tips over #2 (in reverse) and vice versa, but only #2 will disable the left path from #4. This gives #2 before #4 before #1, and don't touch #3.