This is a continuation in a series of posts about writing BBC Basic programs for the @bbcmicrobot twitter bot. In the last post we looked at implementing effects on the BBC Micro using colour cycling with lines. This time we will look at similar effects but scrolling a grid. Setting up the Grid We will jump right into making a small program to draw vertical strips of different colours that we can animate with colour cycling.

This is a continuation in a series of posts about writing BBC Basic programs for the @bbcmicrobot twitter bot. The first few programs I made for the BBC Micro Bot all used the same technique. A series of lines are draw in consecutive colours and then animated using colour cycling. To demonstrate this technique we will go through an example of writing a program to make a sideways scrolling parallax starfield.

Colour Cycling In the last post we looked at some simple graphics commands on the BBC Micro. Typically using the graphics commands on a BBC Micro running at actual speed would be too slow to allow complex animations to run fast enough. In this post we will examine how to use colour cycling to provide cheap animation. We looked at how the command VDU 19 can be used to change the palette of colours.