Make a game about, involving or using instant messages, email, letters, telegrams, smoke signals, semaphore, torn up Valentines, etc. (If actual cryptography is involved you may want to also include some hints because I am not great at that.)

Zooming in:

• Who (or what?) is being communicated with?
• What makes it a challenge?
• How does the medium used to transmit the message influence it?

Your submission can be in whatever format you want: traditional tools are just as welcome as more experimental approaches.

A selection of tools for those looking for a starting place:

Text:

• Twine 1.4/2.0
• Inform 7
• Story Stylus (might work, might not!)

3D:

• Unreal Engine 4 (use the bluprint-based starter projects)
• Unity 5
• SketchFab
• Vertex Meadow
• MagicVoxel
• Sketchup

2D:

• Construct 2
• RPG Maker
• Tyranobuilder
• Manga Maker Comipo