It's very fun but because I can just run away from the TNT and never lose any HP, it was fun more in the Cookie Clicker kind of way where I can't stop playing it only because I want to collect more. Still, I'd say it's enjoyable. The juicy camera shake after every explosion helped with that a lot!
I think something that would make it more challenging is if the TNT boxes you place are, instead, creepers living boxes that chase you and light themselves (and stop moving) when they get close enough. That way, you have to lure every explosive to where you want it to light up. Unfortunately, the AI for this is probably too complicated to implement for just a 3-day jam...