The game is neat, but it seems like the best strategy is just to always solve every level with a single, carefully crafted word that grabs the worthwhile bags on the path to the exit. The game even rewards you 1000 points for doing this! Some reason to prefer shorter words might be a good idea, especially since it is easier to use low-value letters sufficiently in longer words, but in short words it would be much harder not to run out of vowels.
Thanks for your feedback! You're right that there's one clear strategy, which makes the challenge to come up with one good word per level. My feeling right now is that it would be more fun to make doing that more challenging, rather than punishing it or rewarding shorter words, because shorter words are easier to think of.
Another take is that the game needs to make better use of each level, rather than asking you to do just one thing. Maybe I should make players collect keys rather than spelling words of a minimum length.
Fair enough! I think keys would be a better option, probably, because at present the minimum length condition never comes up (all my words are 8+ letters anyhow because that's how long the path is). Maybe you could have to meet some other condition to open the door, like using a certain number of duplicate letters in a word, or using a verb, or using a palindrome, etc? That way there's something other than path length to consider. I don't know how dictionaries for word games work, though, so that might be a stupidly massive amount of work for interesting criteria, in which case keys may well be a better option.