Koi Fish Pond

An idle merge game with a business layer. Koi are released into a pond, each crossing of the finish line pays, and the income funds either more fish or the merges that turn existing ones into higher tiers.

Gift boxes complicate the economy pleasantly. Because fish can arrive free as well as be bought, the optimal move is not always the obvious one — sometimes waiting for a box beats spending everything you have.

It runs while you are away, so the set is built to be checked on rather than sat with.

1. Release your first koi into the pond.
2. Collect the money each lap pays.
3. Merge same-level fish into a higher tier.
4. Buy or collect new fish and repeat.

Merge before buying whenever both are affordable. A higher-tier fish earns more per lap than two low ones, and the pond has limited room.