First off, the game is beautiful. I love the pixel art and I look forward to the finished version. Nice work! Here are my notes:
Gameplay:
It would be cool to be able to use all of your cards on the other team and not just offensive cards. I can't envision a situation with the cards I've seen so far that would make you want to heal your opponents' ships, for instance, but there could be one
It would also be nice to have the option to skip taking a reward card or get money instead of a reward card so that if you have a deck you are happy with you don't have to add more to it unnecessarily.
The fuel mechanic is interesting, and I would like to see more varied consequences such as losing cards from your deck if you run out... "Attacked by pirates while out of fuel! They took your missiles but spared your life!" or you could also implement zones in later stages of the game where the rewards were greater but if you ran out of fuel you would just game over, so you'd have to be very careful if you went exploring there, but maybe you could find unlocks for new ships and cards?
Status indicators:
It would be cool to be able to see enemies applying negative effects visually as damage on our ship and not just in the status text. Likewise, it would be nice to see status indicators to tell if ship is on fire.
It's hard to see that thief drone is doing anything because there is not an indication that you're actually getting any money. Maybe add a little gold +5 money over your ship and -5 money over the enemy?
Balance issues:
Obviously there is a lot of balance to do from an alpha state. As a roguelike it is too easy. The enemies don't do enough damage, maybe, or their damaging effects aren't damaging enough. I was able to exploit the fact that thief drone does so little damage to basically break the economy within the first couple of battles... maybe give each enemy a set number of gold that they can lose, or make the thief drone card have a chance of 'breaking' after each use?
Ringdown removes all shields and disables the entire enemy team... up to 3 ships in the battles I saw. For the same cost, crippling ion only disables one ship and does 2 damage. It may be good to establish a table of value... each effect costs so many points, each amount of damage costs so many points, each effect applied to all enemies costs so many points, etc. Maybe common, uncommon and rare cards could each get so many points worth of effect, if that makes sense.
Thanks! I'm looking forward to seeing this grow.