system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How do they make fireworks that assume a specific shape when they go off?
gpt
Shapes like a circle are easy. You place small charges with delayed fuses around a bigger charge that blows them away from the center point equally in all directions. Shapes like a heart or other more complex ones need the central "spreader" charge to be specially shaped or have some sort of interference so that the smaller delayed charges that makes the shape are the right distance away from the center when the pop.