A cheat upgrade tip: if there are two upgrades of one attribute (hull or damage) you can open and buy only latter(greater) one and get both upgrades (will have to open both if consecutive).
By the 10th level I figured out the "hint" with numbers that grey out not only when conditions are satisfied but when you solve it correctly and it spoiled all the fun. (
For the first upgrade take the flag, for second - speed, cause it allows you to dodge the bullets and flee when it gets hot. For third upgrade I took firepower (+2 cannons) and it allowed me to kill 2nd boss without being hit.
to developers: Concept of "color" cross is not evident. Since most players don't read help (see my comment about number shortcuts) you need additional identification for cross color dependence
What the game needs most is a graphic designer. And not only for visual appealing but to be simply playable.
Now it looks a complete crap. I lost any sense of direction and distance, where I came from and where to go in a minute.
Well,
1) Picma is way better visually,
2) it is more convinient to solve puzzles there since it's automatically marking nimbers in filled rows and columns or parts of it - try to solve a long row or column with lots of small numbers!
3) you can zoom in on parts of the puzzle.
P.S. And don't forget it's great multicolored puzzles!
 "CaribbeanAdmiral")
 "Hands of War 3")
 "NoNoSparks: Genesis")
 "Frozen Candy")
 "LethalRPGDestiny 2: Conquest"){kind=icon}
 "Frantic Frigates")
 "Picma Squared")
 "Hack Slash Crawl")
 "SpaceJunk")
 "Japanese Nonograms")