A few people have asked about particles, so I've created this as a simple tutorial to help understand how really very simple they are. Particles are a short lived SINGLE bit of something. They follow simple rules, they are pinged into existence, live a short life, and ping out of existence. What makes them cool is that if you have a lot of them the effect is fantastic. I've created a controller sprite that just spawns clones. The clone then pings into existence, lives it's short life following some simple rules and then pings out of existence. I would usually do this using a list and storing values there, but this should give you a pretty good idea of how simple and effective this can be. Take a look at the single particle sprite, there's lots of comments to explain what it's all doing Why not remix this and make it do something different, start with a random costume, fade out (using ghost) as it's life gets to the end (just added this feature), cycle colours?
All stock scratch graphics.