That's good to hear, thank you! Hopefully I can keep it feeling an alright level of difficulty as I start to add more enemies.
My current plan to incentivize playing more than one card at a time is with cards that work better if you do so. Like cards that do more damage the farther out in the timeline they're played, or a combo tag that makes cards more powerful when two or more combo cards are played at once, or a card that can 'share' wait ticks with a card played before or after it. That way people who want to play riskier have an incentive to do so, while people who want to play it safe one card at a time can just avoid those combo cards.
If that ends up not being enough, I thought about adding a mechanic that would add 2 or 3 empty ticks at the end whenever you finalize a play. That would incentivize people to play as many cards as they could at once, to minimize those wasted ticks. I'm worried that would feel bad though, like a punishment. I think that's the sort of thing that can only really coming out in playtesting.
I might do that! It would be nice to have someone to bounce ideas off of if you'd be willing.
Thanks as always for your time and for the feedback.