上课展示用的，别看源码，代码写的像狗屎，过段时间删掉 @ParaParty
Idea from @Ezie. Users can drop drift bottles around their location. Drift bottles can be comments to other users or geographic reviews based on location. When other users are within a certain range of the drift bottle, they can open the drift bottle and perform corresponding viewing and interactive operations.
Hidden functions
