Fixed a bug where enemies would periodically become active from stunned state after falling while stacked up. (In the near future, we will implement a visual cue to indicate when an enemy recovers from a stunned status to a different state.)

Added a new Achievement, “Nothing's impossible on the MZ-700!” I thought “I wonder if it's a little bit easy?” but I always wanted to add an exclusive achievement for MZ-700 Mode since it was the first PC I ever bought.