This is the opposite of a building game.

Dwarf Fortress presents a world which decays over time.
The player must build, despite the decay.

Every Sims game invites a player to build with limited resources, then feeds entropy into the system.
The player enforces order.

But the fishtank is order.

The fishtank will right itself.
Every death creates an environment for flourishing later.
The ecosystem will always pull itself back to the same old patterns, held up by a solid inter-linked food-chain.
The fishtank appears chaotic, but it has rules.

The player must break the rules to be free.

The player's job is to get out of the goblin-filled caverns, and their only path ahead will be upsetting the natural balances within the cave.
They must understand the system, then destroy it.

This should feel like the opposite of a building game.
They must play on the system until it collapses in on itself.
