Do you love math? Live in a cold climate? If so, may I suggest crocheting yourself a hyperbolic plane, which is conveniently also wearable as a scarf. It’s a lovely representation of hyperbolic geometry, with the added bonus of being a simple and easy project. I was searching for nerdy scarf patterns when I came across the Crochet Coral Reef project: start with a chain and increase every nth stitch to obtain any number of interesting shapes. Er… no pun intended.
Here’s what the result looks like with bulky weight alpaca blend yarn, a size K/6.5 mm crochet hook, and an increase every 4th stitch. I’m not sure I’m totally happy with the scarf, as I made it too long and it’s rather heavy. I may frog the whole thing and start over with a larger hook, but in the meanwhile I have something to keep me warm and toasty until spring comes back.
Or, with your leftover yarn and a size H/5 mm crochet hook, sc x 6 in a magic ring and increase every stitch to make a hyperbolic pseudosphere…