I have completed this game on Imposible and here are my thoughts.

Pros until now 16/2/2018:
- It's more fun than Galaxy Squadron EX Turbo (a high rated game), for me at least.
- It's like Tyrian, but with a much better balance.
- It has a lot of customization, like upgrades and abilities (called spells).
- It has different ways to play it.
- It has a global success rate on each stage (all players of the game included). I love it.
- You can have a full arsenal of spells.
- You can play a level as many times you want, you get extra money by beating a stage a first time and beating it again with a 75%+ health bar.
- You get money even if you lose on a stage.
- Impossible is more fun than normal.

Cons until now 16/2/2018:
- The worst: the rank/penalization system, you get less and less money by getting more money. The minimum is to get a 0.2% of all the money that you get, from rank 32. And you are kind of limited to 95000 aprox., after that is too hard to get any money at all, so you can't have an all powerful spaceship, specially if you want to experiment, and you waste money in something you don't want. (With higher ranks you also get higher levels of spell upgrades, and you can unlock the mastery upgrades, so not everything is bad about it). The penalization is kind of balanced until you reach later ranks.
- 31+ is a chore to try to win any money at all.
- The stages colors look too dark, specially on the first levels if in your room there is sunlight.
- There isn't keys customization yet.
- There isn't as many passive upgrades as spells upgrades there are.
- Auto-cast (A key) needs to have a priority list.
- You can't be trully overpowered.
- Gaunglet isn't very fun on impossible and it's very hard, specially for the low money you get by playing it at higher ranks.

I think it's is a very well made game, thought the penalization system isn't good to me after playing a lot of the game, because becames the game too repetitive, thought I understand why they wanted to limit the money, but I don't like that decision.

I would buy an expansion, if there was one, and I think the money is well spent at full-price (even when I usually buy games at super low prices).

I had a lot of fun playing it. So I recommed it.