The universe might be a simulation, as the favorite sci-fi trope goes, but this is almost impossible to prove or disprove from within the speculative simulation. What is surer is that our universe is full of simulations. Whether those are computer-generated predictions and projections we increasingly use to look ahead or the natural forms of mimicry and camouflage deployed in the elaborate dances between predator and prey. Meanwhile, humans explore the possibilities and risks available to us via every sort of test run we can devise.