Lots of fun. Also lots of bugs. Never got rewards for most of the achievements (including the entire line of no damage / no shooting series). x2 coin visual got stuck on for a while after pausing with that bonus active (did not actually get 2x coins). That said, enjoyable game. Bugs will get ironed out in time, hopefully.
Really good game. Well-timed spells (& grinding, ofc) are key to progressing. Customize skills for each area. Upgrade life, attack, and defense wisely; a different one will be the best value at each level up. Don't neglect attack—quick kills are key early to save spells for the tougher enemies.
Something that would be very useful: being able to toggle different branches of the tech tree on or off. I don't need to research all 4 weapons and 3 energy sources. I'm good with 1 of each, but I'm not going to manually sort it at each step.
Other possible gameplay improvements:
Make the WASD and/or arrows hotkeys for the tower upgrade/shield/sell/repair menu. It would make it much easier to get things done with a wave of monsters bearing down on you. Mission 13 in particular comes to mind, where it's just one long wave.
Finally beat all 15 levels on Ultimate Mode! Love the game, pretty well balanced overall, but I think the amount that you can sell a tower for should scale with how much HP it has remaining. Too easy to wait for it to get down to 10% health or so then sell it for 80% of it's value and use the cash to build a new one in the same spot.
Great concept, needs lots of balancing. Critical hit is over-powered. Fortress is under-powered. Treasure maps are too easy. Computer's combat AI needs a lot of improvement - it'd be better if it just moved all ships toward the human player each turn. It'd be predictable, but it'd never lose 6 ships and 3 fortresses to my 4 weaker ships if that were the case.
Thanks for the comment, I'm running out of time to fix these bugs. Thanks for playing, I will look into the coin bug. Thanks.