Traditionally, on the bottom of each shell is a lift charge. When ignited that charge propels the shell out of the mortar like a bullet is fired from a gun. When the lift charge goes off it lights a little internal fuse, this fuse is timed to burn for the amount of time it takes for the shell to reach burst height. Usually, a shell goes up to 30m for each 2.54cm of diameter. Thus a 10.16cm shell bursts at 120m. Inside the shell is another burst charge, this blows the shell apart and sends everything inside out in every direction equally. Such that if one were to place ” stars” in a smiley face pattern, the face will grow and keep its shape throughout its burst cycle. Stars are small pellets of pyrotechnic composition and shavings of different metals about the size of a skittle. When the shell bursts apart it's so intense the pellets ignite and burn. Different metal components burn different colours and degrees of brightness. To start this whole process, there is often an electric match embedded in the lift charge. This is connected to a wire strip, which connects to the firing panel. A stylus is touched to a metal sensor to connect power to complete the circuit.