Rain Drop starts out as a single particle in the upper atmosphere. There are water molecules dancing around due to Brownian motion, as you collect them you start to fall. Your goal is to make it to the ground. You collect more and more droplets but there are obstacles that are preventing you from hitting the ground and watering the plants. Dodge the obstacles, collect the other droplets and make it all the way down while chilling out to a chillwave soundtrack.
The game takes place in a futuristic cyber dystopian style series, imagine if every Rain Drop in one of those movies had it's own journey dedicated to it.