My game, Shadow Physics used Lua as a serialization format as a side effect of the game initially having no level editor or level import capabilities, only Lua

My game, Shadow Physics used Lua as a serialization format as a side effect of the game initially having no level editor or level import capabilities, only Lua scripts to create levels procedurally. Copy and paste was also implemented using Lua, a fun side effect of this you could copy and paste arbitrary Lua code as a live coding technique.