This has some really fun mechanics, it's a shame you didn't have more time to balance it out. Still, by the end of my playthrough I was enjoying just tinkering around with different card combinations. As you can see in my screenshot below, I had started making an automated point generator setup. However, I started to have some visual bugs with cards doubling up in slots and drawing at weird offsets. The late-game stuff is really fun though, you could definitely develop something bigger with this. 

The early game was a bit slow though, I'm not such a fan of putting a cooldown on a clickable like the draw and submit buttons; either clicking or a timer is fine but both isn't so much fun. Also, I wonder if the shop stuff could fit on the same screen as the play area, just to save some clicking in and out of them?

Wow. At first it was a simple incremental where you use color to buy upgrades but after you unlock x cards the whole game changes. In this case you start building massive chains of multiplication cards in order to rack up tons of color. It feels real great to do these combos. The rare cards seems to be possibly a too big of a step up and the rng in getting good cards could be a bit frustrating especially since the scaling of card packs is a bit messed up, eventually your game kind of becomes soft capped where cards become to expensive and take too much time to grind. Either way its really fun to play and I had a good couple of hours playing this game. Great Job!

Some neat ideas here, and the game really reveals itself over time as you open up the mid and end game upgrades.  Opening up board slots feels very good as that allows you to make stronger and smarter plays, an alternative to how the genre tends to just hand you multipliers for growth.

One of the mechanics that was the most interesting was having card removal as a card itself. It was a good way to enforce the positioning-theming even harder and worked well. Unfortunately that did make me scared to use the green automation later on, as that would've crippled my deck over time I'm sure.

While lots of bold ideas, at the same time some ideas clashed. I know you were looking to find more upgrade vectors for each color, but some of the idle waiting mechanics clashed with such an active game. Luckily that stuff gets obsolete over time, so I suppose there is a nice pain point removal once you get those upgrades high enough.

The end game cards are really fun to use and there's a bit of thought in figuring out how to balance your deck (as any deckbuilder should). Like you said in your description, there's a few builds and strategies and that keeps it all interesting. Nice work :)

Dragging the cards is hard to do