Particles is a simple simulation of the motion of up to 1000 'particles', pixel sized entities. Using simple motion formulae the positions and speeds of each particle is calculated and plotted.

Variable gravity is included such that the force of gravity may be varied in both the vertical and horizontal directions in real time. The number of particles in view may also be changed, taking any value up to 1000.

The program can be set into two modes. In the first 'box' mode the particles are randomly distributed at the start and from then on are confined within the 'box', bouncing of the walls. The walls all have a small coefficient of restitution so that the particles (if left with the same gravity settings) will slowly move towards a standstill as energy is lost with each collision.

The second mode is a fountain effect. Here the walls of the 'box' have been removed so particles may leave the area but particles are generated from a set point with a random (positive) vertical velocity and a random horizontal velocity in order to simulate the fountain.

Having been through several stages of development, Particles is now at Version 4! (213kb zipped). As in version 3 the entire surface of the window has been utilised and the controls can be made invisible or visible at will by clicking on the background. Now, however, you can also remove the borders of the window and make the cursor invisible. Just maximise, enter your favourite settings and click... instant screen saver!

Also, by popular request, 'vapour trails' have been added. Each particle leaves a trail of adjustable length which fades over time. Be warned, hoever, long trials lead to slower motion (it does on my computer anyway!).

This is probably as far as I will take the Delphi version but future versions may well be produced in Visual C++ and possibly Visual Basic... C++ produces a more efficient emulation and appears to produce a program approximately a tenth the size of its Delphi equivalent so it will be put up here as soon as it has been polished. VB produces a much slower program (even without double buffered animation) and requires the download of Microsoft's virtual machine and any ActiveX controls I have used. Maybe not.

The file above is in zipped format and you will require an unzipping program to restore the executables. Winzip is available for Windows operating systems.