/* vim: set ft=c: */

# define M_PI              (3.141592653589793238462643383279502884) /* pi */
# define M_PI_2            (1.570796326794896619231321691639751442) /* pi/2 */
# define M_PI_4            (0.785398163397448309615660845819875721) /* pi/4 */

/* <https://www.shadertoy.com/new> */

void
mainImage (out vec4 fragColor, in vec2 fragCoord)
{
    const float t = iTime;
    const int T = int (3 * (0.5 + 0.5 * cos (t)));

	// Normalized pixel coordinates (from 0 to 1)
	// vec2 uv = fragCoord.xy / iResolution.xy;

	// Texture coordinates
	vec2 uv = TexCoords;

	// float du = 1.0 / iResolution.y;
	// vec2 uv = du * (fragCoord.xy - (0.5 * iResolution.xy));

	// Time varying pixel color
	vec3 z1 = vec3 (
              sin (t)            * cos (t)
            , sin (t / M_PI)     * cos (t / M_PI)
            , sin (t / M_PI / 2) * cos (t / M_PI_2)
    );
    vec3 z2 = uv.xyx;
    switch (T)
    {
        case 0: z2 = uv.xxx; break;
        case 1: z2 = uv.yyy; break;
        case 2: z2 = uv.xyx; break;
    }
	vec3 col = 0.5 + 0.5 * cos (iTime + z1 + z2);

	// Output to screen
	fragColor = vec4 (col, 1.0);
}