This one is a bit out there, but I feel like Backpack Battles is a series of self-generated puzzles.

It's an autobattler where you shop between each round to buy items and bags, and items affect other items in specific positions around them. So, you're constantly trying to react to what the shop is offering you to build a combo (and get balanced defenses), then rearrange your bag to try to maximize your item synergies.

It's completely free to play in early access until its full release in April. And the global leaderboards are very active. Good luck getting to Master Rank, let alone Grandmaster! (I've plateaued in Diamond... I need to work on my early game.)