You should be able to click on cards to play next while one card is playing - was it not working for you?
For the icons, do you think it was the shape or the color that was too similar?
I can play them sequentially without trouble, yeah, but what I had in mind was playing them simultaneously. Like, instead of a queue system, there would be one animation playing, then another right under it. I presume the computer already knows what happened the instant you use a card, and the animations are artistic flair. It's not a huge deal since animations can be accelerated so much in the settings, just a matter of personal taste.
The icons for Growth and Energize are both green, three-pronged objects "pointing" left. The upgrade/buy sections are "zoomed out", for lack of better terms, so evidently I wasn't paying enough attention to notice the difference. The kicker is I can't think of something else either of them could be. A plant is a perfect representation for growth as a concept, and the icon for Energize is almost the same as for Energy, just recolored and tilted in a different direction. It's a tricky situation, this. Sorry I can't be more useful. Goes without saying, but don't feel pressured to change the game on my behalf. I'm just one man.