The basic premise of the game is that each level is an island which is slowly sinking into the sea. The player must therefore get to the top of each level, by jumping on platforms and making use of the game's most distinctive feature: the ability to produce solid rainbows, which are used both as platforms to stand on, and as a weapon (remember the case in Bubble Bobble when using gum bubbles for the same reason!).
While initially appearing to be quite a simple game, Rainbow Islands in fact has a vast number of secrets for the player to discover, including secret levels, secret power-ups and riddles. Because of these elements, completing the game properly requires a large amount of dedication from you, especially when sprite animation and background scrolling show some glitches on the Spectrum (and CPC) port.
The ZX version runs on 48k and 128k hardware. It features nicely drawn graphics with great colors (!) much like the CPC and C64. Most of the detail is ported successfully from the (arcades) original version. Although sprites look cute and nicely detailed, animation shows some glitches whilst scrolling also has problems here. Eitherway the game looks amazing for a ZX Spectrum game!
Soundwise, the 48k Spectrum version offers the original intro tune at the main menu only (and limited to the older YM sound chip) whilst there are a few dull SFX during gameplay. On the other hand, when running on a 128k or a +2/+3 model (with the more advance YM YAMAHA chip) it offers the original superb soundtrack during gameplay along with the few cute original (!) sound effects. You may listen to the 48k tune as an intro or the 128k tune as an in-game sound below.