Puzzles are allowed to have transparent parts as long as they do not …

…provide additional information (#1029)

* Add examples to 3h2a

* Update wca-guidelines.md

Co-authored-by: Lucas Garron <lgarron@worldcubeassociation.org>

Co-authored-by: Lucas Garron <lgarron@worldcubeassociation.org>

wca-guidelines.md

@@ -71,6 +71,7 @@ To be more informative, each Guideline is classified using one of the following
 - 3h+) [CLARIFICATION] Puzzles may be refined internally by sanding, lubrication, or modifications which improve stability (e.g. magnets).
 - 3h++) [EXAMPLE] Examples of enhancements include: new moves are possible, normal moves are impossible, more pieces or faces are visible, colors on the backside of the puzzle are visible, moves are done automatically, or the puzzles have more/different solved states.
 - 3h2++) [CLARIFICATION] "Stickerless" puzzles that significantly differ from most mass-produced "stickerless" puzzles are only permitted at the discretion of the WCA Delegate.
+- 3h2a+) [ADDITION] Examples of transparent parts that do not reveal more information about the state of the puzzle: internal parts of the puzzle mechanism, transparent Clock cases.
 - 3j+) [REMINDER] In the past, engraved/embossed parts have been permitted. This is no longer permitted.
 - 3j++) [CLARIFICATION] On Clock, pins may be distinguishable from any other pin of the same side.
 - 3j1+) [REMINDER] On Clock, loose pins (i.e. pins that can toggle or recede using gravity instead of being directly pressed)  are not considered reasonable wear.