Heartland's meta-referential plot involves a struggle between good and evil, as depicted in a book, the last six pages of which have become lost. As a result, you must dive into the game's world to complete the story, and ensure that evil doesn't win, by saving the white pages and destroying the black ones.
There are six levels, all with distinctly cutesy themes and colourful graphics. The level layouts are extremely complicated, and you have to make your way back to base after each one, before being transported onto the next one, all within a time limit. The levels are full of wizards who must be shot, as well as a small amount of character interaction.
The Spectrum version of the game reputedly crashes when the final page is collected, so you don't get to see an end sequence - to appreciate how ironic (and perhaps intentional) this is, re-read the description.
The makers used a trick in the Spectrum's screen format to hide text in the loading screen with the credits of the game's creators, since Odin did not allow personal credits in their games:
C.GRUNES.; GAME DESIGN AND GRAPHICS C.GRUNES; GAME PLAY AND PROGRAM MAX BOUNTY COUNT; GRAFX-C.GRUNES CODE-MAX.B.COUNT.