Firework rockets are items and entities which, when activated, create colorful explosions. The color, fade, shape and effect of the explosion are determined by what ingredients are used to create the firework star - one of the ingredients used to create a rocket. However, a firework rocket can be crafted without a firework star. When this happens, it will only have a rocket trail, with no colorful explosion. The height of a rocket can be altered by adding up to 3 gunpowder to the rocket recipe. This increases the flight duration by 1 per gunpowder. Multiple firework stars can also be used, in which case each one will go off simultaneously when the rocket detonates. Firework rockets can be activated by right-clicking any block with them, or they can be fired out of dispensers. The fireworks are customizable in colors, shapes, and height. There are 336 different kinds of rockets. Their flight path is random and sometimes are offset up to 5 blocks to the side, they also tend to spiral up. Fireworks are also affected by gravity. Their motion can be changed with TNT or flowing water.

There is a delay between detonation and the player hearing the sound, emulating real fireworks, but this sound travels much more slowly than in the real world.[1][2] Jeb mentioned on Twitter that fireworks may have effects on mobs, such as scaring wolves.[3]

If a rocket's path is hindered by any solid block it will do one of three things: stay under the block as if caught there until it explodes (more likely to happen if the firework has a shorter flight duration), explode upon contact (if this happens the explosion will appear above the block, even though the rocket did not go above it, unless there are more than one block), or stay under the block for a few seconds then fly off more to the side (more likely to happen with longer duration). If a rocket with any kind of explosion ingredient detonates under a block, the explosion pattern will appear flattened against the ground in a wide, disc-like fashion.

http://minecraft.gamepedia.com/Fireworks

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