flockaroo 2018-03-12 cool, i already wanted to do some tutorials for people to get warm with it... :-)
but for "default:" i would even suggest to set vertCoord to vec4(0)
because otherwise on some systems a lot of unintialized vertices could be spawned which could result in a lot of random drawing action and stall the system.
Buffer
void mainImage( out vec4 fragColor, in vec2 fragCoord )
{
fragColor=vec4(0,0,0,1);
}