fragment shader

// fragment shaders don't have a default precision so we need
// to pick one. mediump is a good default. It means "medium precision"
precision mediump float;
 
void main() {
  // gl_FragColor is a special variable a fragment shader
  // is responsible for setting
  gl_FragColor = vec4(1, 0, 0.5, 1); // return redish-purple
}

vertex shader

// an attribute will receive data from a buffer
attribute vec4 a_position;
 
// all shaders have a main function
void main() {
 
  // gl_Position is a special variable a vertex shader
  // is responsible for setting
  gl_Position = a_position;
}