A complete list of literally EVERYTHING that an observer can detect. Hopefully at least... Research was crazy...

Chapters:
00:00 Intro
00:28 What does an observer do?
01:51 The Common Denominator
02:20 Building Blocks
03:21 Colored Blocks
03:57 Natural Blocks
10:08 Functional Blocks
12:10 Redstone Blocks
15:31 Broad Categories
16:59 Special Cases
17:51 Outro