I finally sat down and started work on my game after coming up with the concept at the beginning of the jam and then doing Nothing.
The concept is a CCG where your to-do list is the deck and each task is a card. I'm still working out the mechanics, but you would write down your task on an index card, write the estimated time it takes to complete it, and then the actual time; cards with an estimated time close to the actual time have a higher attack, and cards that take longer have a higher defense.
Three variants for play: one where you only play with task-cards that are completed, one where you play with a mix of task-cards, but you have to complete the task within 6-12 hours of playing it (or some other time limit agreed on by the players), and one where you only play with task-cards that are not completed, trade decks, and when you play a card, your opponent has to do their task on the card–and vice-versa.
This is my *sixth* to-do list game concept, but the first that involves playing against others, so it's a new and interesting challenge.