I didn't understand this game at first, even after the tutorial, but once I got into the game I got REALLY into it!
The deck system along with the one-on-one boss battles was an interesting twist on the standard bullet hell genre. I can see that concept scaling into a full game well, with booster packs opening up new skills each time you defeat a boss and progress the story. It even makes for self-imposed difficulty settings. Are you highly skilled at this game and want to beat the boss down fast? Pack as many big attacks as you can. Are you a noob? Pack in a bunch of heals and buffs and you'll be good to go!
The music is excellent pulse-pounding energy music, perfect for the mood of the game. Sound effects were good for the most part, though I would have liked to hear something when the aimed shot and homing missiles connect with their targets.
I liked the character designs and UI overall too. Characters are clear and fun to look at, and the UI is arranged in such a way that I never felt like important information was hidden (except for the between-turns dialogs) or buried in menus.
There are some things that could be improved:
The dialog between the characters between turns is too long and it's not clear when the exchange is over (I eventually learned to recognize the tiny arrow that appears under the boss' text area when the dialog was done). That said, the exchanges were kinda amusing and have potential for even more interesting exchanges as the plot develops. I also appreciated that the dialogs can be skipped if I'm not interested.
It's hard to recognize which attack is queued up when you're on the field because the icons are similar color and kind of small. Furthermore, it's not clear how to aim many of them. X Beam is nearly useless because I'm not sure where the beams will be relative to my character and the enemy. I eventually got the hang of most of them, but it was a turnoff initially and could use some quality of life improvement.
Overall this is a great start to a larger project and an outstanding entry.