A one-button real-time puzzle game for the Commodore 64 and unexpanded Vic-20.
The Vic-20 version won the 4k category of the 2011 minigame competition. The C64 version came 6th out of 17 entries in the 2014 RGCD 16KB Cartridge Competition.
You can play the Vic-20 version of Fickle in your browser.
Discussion about the Vic-20 version is here and about the C64 version is here.
My friend, Ben North, created AutoFickle to solve Fickle levels. Interestingly, it interacts with Fickle via the Vice Vic-20 emulator.