Played levels 1 and 6 with a mouse. Watching the fire crawl along the oil and flare through the torches is a good payoff, and the Undo button on the BOOM card means testing an idea costs nothing. On level 6 the keg sits on its own trail with no torch on it, so avoiding it takes no thought. By that point I'd have the keg share a trail with a torch, so you have to pick where to strike.
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Thanks for playing, and you're right. After reading this I checked all 30 boards: on levels 4, 5, 6 and 10 to 13, every keg sits on a trail with no torch on it, so the keg never changes what you strike. From level 15 on, every keg shares a trail with a torch, which is where the puzzles get good. My level picker doesn't check for this yet. The post-jam update will add the rule you describe (every keg has to share a trail with at least one torch) and replace those early boards. I'm holding level changes until AI Jam 5 voting closes.
The fix is live now (v2.0; the jam host said updating during voting is fine). Every keg left in the game now blocks a strike that would also light a torch. The rule ended up a bit different from what I promised: on the no-wind warm-ups (levels 4-6) a keg can't sit next to a torch trail without making those torches unlightable, so those levels lost their kegs instead. Thanks for catching it.