Eat the right thing at the right time.
Willy the earthworm was minding his own business at the bottom of the orchard when he ate the wrong apple. A spiteful old witch had cursed it, and now, whenever the moon rises, Willy becomes a Wyrm.
By day he is a pink, vegetarian worm in a muddy garden, after apples and garden greens. By night he is a golden, carnivorous serpent on moonlit flagstones, and he craves meat. The food on the board stays exactly where it is, so whatever was dinner a moment ago may now be poison. Eat the wrong thing and the indigestion sends your controls the wrong way.
Ten apples. Eight orchards.
Only daylight brings the end closer. Eat ten apples by day to clear an orchard; clear eight to break the curse for good. Nights are for surviving and scoring. Everything you eat makes you longer, and your length carries from one orchard to the next, so every snack is a decision you live with.
One more go
Easy to pick up, and the orchard you almost cleared is always the next one. Pause when you need to and chase your high score: the Amiga keeps it for as long as the machine stays on, and the BBC Micro saves it to a writable disc. A Commodore Amiga original, with a BBC Micro edition written in 6502 assembly.
