Handicap

"Perverse" problems, that place some arbitary handicap on the programming.

E.g.

• Source must be in uppercase only : CALENDAR
• Not allowing certain datastructures: strings/arrays/... : Odd word problem
• Restricted I/O
• No comparisons, arithmetic, no lists, no re-reading of input : Longest string challenge‎
• Code golf challenges : Game of Nim

...