Payment is one-time, not recurring, and handled by Stripe. $5 USD is the minimum, but you can pay more if you're feeling generous. Paying once gives you access to all previously published puzzles until the heat death of the universe, or the game becomes insolvent, whichever comes first.
If you want to know more about who you're giving money to, you can learn more about us here.
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Puzzle Hint
A hint will reveal a letter that lies at an intersection (for the intended solution).