I remember designing a game on my Vic-20 not long after I first started writing programs for the wee beastie. It was an overly ambitious game, given my sorely lacking skillset at the time, but I remember part of the premise: You had to parachute onto an island, guiding your character to a safe landing a la Lunar/Moon/Jupiter Lander. Once on the island, you had to locate several items then build a raft/boat before navigating your way back to the mainland. It would have been a cool little game and I did get some initial code written but never got beyond the initial parachute stage. (And even that didn’t work quite as I intended. 
) I found a couple of the initial sketches I made for the game when I was digging through my Vic-20 stuff the other day…
My next foray into game programming was more successful, though much less ambitious. It was for the Commodore 64 and was my first attempt at using sprites. The concept for this game was very simplistic – you controlled a hand holding a can of fly spray and you had to spray as many flies as possible in 60 seconds. I drew all the sprites on graph paper and laboriously calcuated the correct values to POKE into memory.
I didn’t actually own a Commodore 64 of my own at the time – I would write the code on my Vic-20, save it to tape, then take it around to my friend’s house and load it up on the Commodore 64. Surprisingly, the game worked first time and we had a lot of fun playing around with it. 
After that success, my game-writing career turned to text adventures and I never quite reached the heady heights of graphic prowess of that original Fly Spray game!