The coins cost for playing a puzzle should based on the total cells instead of the longest side. Like 100 cells and fewer for small, 125 to 625 for medium, 675 to 1225 for Large, and >1225 for Extra Large. For example: a 20×50 puzzle have 1000 cells, so it should go to "Large" size, not "Extra Large".
Unoffical FAQ
Q: Why the News Station did not got attacked?
A1: Because the station is you ally, just like the shop for upgrades.
A2: Because you did not choosed, or do not need to attack it to conquer the world.
A3: The reporter is just a screen.
In the new version we are seriously considering changing the size classes to use the total area!