This game was actually really enjoyable...
It's a puzzle game that pushes a lot into min maxing as part of a strategy or gimmick...
It doesn't completely rail road players since I read a couple of strategies that I didn't personally do...
but... it kinda does... per say when using upgrades...
BUT, I think that's part of the puzzle of the game -- since it allows players the choice and also learn what works and what doesn't with every retry... I often figured out the gimmick of a level by the 15-20th try (given the first 5 are always just increasing army size)
The first wave will always be a time to test out each of your units (although it isn't always clear what they do) and after the first wave you'll get to see the upgrades you're dealing with. You'll always get 60 gold on the first wave, so it's always best to just buy the first army size upgrade (along with an upgrade of your choice) There's a certain agency to using the last 20 gold for a "usually" meaningless upgrade and be short to upgrade army size during the 2nd wave... but its not always the case... (damage > army size > other upgrades is generally the prio order)
You won't always be able to figure out the gimmick early on, meaning sometimes you start putting upgrades in worthless stats, but again, I think thats why its fun to learn through trial and error, and repeat/reset the level once you've got an idea and want to run with it!
For those looking for tips:
Fighter -> Flank (Shield Units in Front, Attackers in the Back)
Mage -> Box Formation/Ranged Flank (Draw Fire using the Support Unit, Range Attackers from the Back)
Rogue -> Perma-Root (Alternate spawning the rooting and attacking units to stunlock)
NOTE: I actually really enjoyed this one, some people may have found it hard, but its the first one that required quick swapping between units; which wasn't a mechanic that was required in the previous 2 levels.
Priest -> Corral her into Puddles
NOTE: This was probably the slowest and most boring level, simply because the pathing won't always be your friend and it can get frustrating and tedious; but it's not too bad -- its a change of pace, I just feel like it should've been before the rogue level; because the rogue level was fun due to its fast paced nature and this level does a complete 180...
Princess -> Shield the Backline
Demon Queen -> Four Corners & Capture On Yellow
NOTE: This apparently frustrated a lot of people, because it changed up the timing for capture. Up until now, all levels did not punish players for capturing on red. Actually it usually rewarded players by incentivizing farming on red. Leading to a very simple capture strategy when players know they can get enemies to red. This changes it up by punishing the player when she's in red. Just try to capture on yellow, or get her to red and start letting her regen.
Anyway, this was enjoyable -- I wish there were more scenes or more h... but as a game it was solid.