Solution for The Deep
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Light blue atoms: The default atom. They add to your score and add a new explosion that keeps the reaction going.
Dark blue atoms: Slow moving and turn around a lot. Collecting them spawns ten new light blue atoms at the sides of the field. Collect these as early as possible.
Red atoms: While red atoms do add to your score, the red explosion they leave behind is bad news - any atoms touched by it are destroyed without adding to your score. Most levels with red atoms require you to collect them - the trick is to always have a blue explosion nearby that you can steer other atoms into.
White atoms: Give you an additional click with which to start a new reaction, but don't explode and don't add to your score.
Yellow atoms: Turn your cursor "magnetic" - it attracts rather than repels atoms. Collect a second yellow and the effect reverses. I don't think these explode. Keep track of them, because if you collect one and don't realise it, you've probably lost by the time you've worked out why the atoms aren't behaving as they should.
Brown atoms: Cause you to immediately lose.
Green atoms: Behave just like light blue atoms, but every time one is collected, every other atom speeds up slightly. Avoid for as long as you can, they make the game ridiculously chaotic.
Ochre atoms: Increases the time that the ring kept open.
Purple atoms: Slightly increase the radius of the rings.