# Introduction to Colliding Complex Shapes

In these tutorials a complex shape is one constructed from spheres of the same size in such a way that any one sphere
is always in contact with at least one other sphere in the shape. A complex shape is likely to have concave sections.
Multiple shapes will be constructed using the Solid Particle System because of the speed and flexibility if gives to using
many similar shapes.

The aim of this series of tutorials is to develop a way of using just BabylonJS code (ie no physics engines) to simulate the the collision of complex shapes. The series will start with looking at the issues involved in collision and (hopefully) end with a full collision system.

To begin with the frame rate will be taken as constant throughout the animation and speed for any shape will be in units per frame.

## Index

Speed and Size Collision Issues

Simple Particle Collisions on a Grid