DOODLEBUG
by Paul Morris
for 1K/16K Sinclair ZX81
published in "ZX Computing" magazine (England), Oct/Nov 1982, p. 69

The computer prints a cursor which can be guided around the screen with
the arrow keys. This is not very unusual or original so far, but look what
happens when you press a letter key. It is displayed on the screen where
the cursor is.
  You can use this to produce interlocking patterns of words on the
screen, to insult you favourite enemies, or to pass on messages.
  Paul suggests another application - to build up crosswords, with any
mistakes erased by backspacing with the cursor. With 1K, you can use 17
lines of the screen.