If you really wanted to make an interesting twist to this, you can base sufficiently hard levels/an extra level pack off of the (1,936, if I remember correctly) 'irreducible configurations' to which Appel and Haken reduced their proof of the Four Color Theorem.
It would help if the upgrades purchasable in the headquarters also had x1, x5, etc., buttons for speeding up the process when we want to buy them in bulk.
If this is a bug, it's very minor:
I was up to Aura Radius XVII (if I read correctly), and the next ability being researched displayed as Aura Radius XIX. What happened to XVIII?
It appears that increasing one's size adds 50% of base max HP to one's current max HP. Since this does not change the underlying base max HP, only the first time does this multiply the max HP by 1.5. Please don't confuse linear and exponential growth.
What am I missing, regarding level 12? The first move is either yellow up, yellow left, green up, or green right. If the first move is green right or yellow left, you pinch off the two bottom tiles on that side -- either you go to them and can't return, or you ditch them for everything else and can't reach them later. If the first move is yellow up, green is cut off and cannot reach its destination. If the first move is green up, yellow is cut off and cannot reach its destination.
Did something glitchy replace level 12 with an unsolvable variant, or am I just missing something?
One of the new tiles in this game is the explosive tile. With this one, there's a 'purist' feeling that maybe it's good to give a little extra reward to someone who completes the level with as few detonations as possible.
Killing everyone makes it harder to build up health by going back for guards or scientists who were spared. One way to make that more necessary is to have an adjustable difficulty -- the higher the difficulty setting, the less health you have when you begin an area or restart from a checkpoint.
Please add hotkeys! Having to frequently go back and forth between keyboard use and mouse use is worse for one's hands than sticking with the keyboard.
Bug: I have built > 200 Gardes Francais (but fewer than 500 of them), and the price for hiring one is listed as 85 in the battle menu. However, when I see how much I pay, I'm being charged 95 for one of them.
Thank you for the advice. Now that the game is understood by a good amount of players I'm planning on adding more challenging levels.