Tips:
Collecting all of the gems in the correct order of color
(from left to right on the gem counter - RED, ORANGE,
YELLOW, GREEN, LIGHT BLUE, DARK BLUE, and MAUVE) not only
awards you the life and Bonus Gem, it also grants you access
to a magical secret room. When you reach the end of the
level, a silver door appears. You don't have to fight the
Boss.

On the fifth island you'll find a box in the secret room
which you should collect. There's also a gate with a '7' on
it, leading to Island 7

Even more useful is how to create any color gem. The screen
is split into several invisible vertical stripes of color.
When a gem falls, its color is determined by the `color' of
the area into which it fell. Now all you have to do is
gauge carefully where the dead enemy will fall to create the
gem color of your choice.