Gems are fun. They’re not even really an obstacle, per se, except inasmuch as sometimes you don’t get as many as you need to for a prompt clearing of the level. Otherwise, they’re great: they’re relatively easy to clear, they destroy a bunch of other dots (or slime, or ice, or beetles, or blocks) when they go, and they just look cool when they go off.
When you clear a gem that’s a horizontal rectangle, it clears the entire horizontal row. When you clear a gem that’s a vertical rectangle, it clears the entire vertical row. When you clear a square gem, it clears both the horizontal and vertical rows intersecting with the gem.
Gems can be cleared by making squares of a matching color, or by hitting them with bombs, blasts from other gems, and cloud zaps. Not too hard.
You don’t even really need strategy with gems, unless clearing them will release fire or slime. If that’s the case, pause and think. Otherwise, clear away!
If this guide helped you out, please consider buying one of my books from Amazon. Here’s one: Side Effects, the story of a doctor who just wants to help his patients, even when the government and the free market doesn’t want him to. Don’t worry; it’s not a polemic. I promise.