所有升级的收益都被降低，花费部分上调，僵尸的强度则继续增强。
The benefits of all upgrades are reduced, the cost is increased, and the intensity of zombies continues to increase.

现在变态难度变得更变态了，防御塔升级更难了。
Now the extreme difficulty has become more extreme, and it is more difficult to upgrade the defense tower.

增强了最高难度下的僵尸强度，同时调整了部分数据使其更加合理。
Enhanced the zombie intensity under the highest difficulty, and adjusted some data to make it more reasonable.

新增了两个特殊升级
Two special upgrades have been added

增加了20天的尸潮提示信息，引入两个特殊升级
Added 20 days of zombie tips and introduced two special upgrades

突然发现忘了加油田。
Suddenly found that I forgot the oil field