Like the title says. Actually you don't have to tunnel all that deep. Just a bit of navigating a couple of tunnels. Here's a hint. Don't be afraid to have to go get a new cube. We have warehouses full of them. I'd say it's about medium difficulty.

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Yay, a funnel "labyrinth", never gets old. And it's great that there are no laser fields involved, avoiding your daily quicksave fest.