To unlock nightmare mode, you need to reach 107 level. The nightmare mode starts with 17 bales of grass, and reasonable use of 17 bales of grass can win at one time. It is suggested that 17 bundles of grass should be picked up at the altar. First, catch 7 sheep with 7 bundles of grass and throw them near the altar, then catch 3 sheep with 3 bundles of grass, one in the hands of two people and one in the pot (you will catch 10 sheep). The remaining 7 bundles of grass will be used to quickly catch 7 sheep near the altar and put them in the pot in turn to burn.