const highp float PI = 3.14;
const highp float TARGET_COUNT = 15.0;
const highp float GRID_CELL_SIZE = 0.1;

highp vec2 getGridPosition(in highp vec2 uv) {
	return vec2((uv.x / GRID_CELL_SIZE), (uv.y / GRID_CELL_SIZE));
}

void fragment() {
    // Normalized frag coordinates
    highp vec2 uv = 2.0 * FRAGCOORD.xy / vec2(1024) - 1.0;

    highp vec2 gridBoundUV = getGridPosition(uv);

    highp vec2 cellBoundUV = gridBoundUV - round(gridBoundUV);

    highp float redIntensity = 0.0;
    highp float blueIntensity = 0.0;

    for (highp float targetIndex = 0.0; targetIndex < TARGET_COUNT; ++targetIndex)
    {
        highp float f_targetIndex = targetIndex;

        highp float trigOffset = (PI / TARGET_COUNT) * f_targetIndex;
        highp vec2 targetPosition = vec2(sin(TIME + trigOffset) * 0.51 + tan(f_targetIndex + trigOffset), cos(TIME + trigOffset) * 0.1 + sin(f_targetIndex + trigOffset));
        highp vec2 gridBoundTargetPosition = getGridPosition(targetPosition);
        highp vec2 edgeBoundPosition = vec2(gridBoundTargetPosition.x, gridBoundTargetPosition.y);

        // change the op between the lengths to subtraction for some extreme strobe effects
        highp float distanceToTarget = length(gridBoundUV - round(gridBoundTargetPosition)) + length((gridBoundUV) - (edgeBoundPosition));

    	redIntensity += length(GRID_CELL_SIZE / (distanceToTarget * 9.5)  / cellBoundUV) * GRID_CELL_SIZE;

    }

    for (highp float targetIndex = 0.0; targetIndex < TARGET_COUNT; ++targetIndex)
    {
        highp float f_targetIndex = targetIndex;

        highp float trigOffset = (PI / TARGET_COUNT) * f_targetIndex;

        highp vec2 targetPosition = vec2(sin(TIME + trigOffset) * 0.51 + sin(f_targetIndex + trigOffset), tan(TIME + trigOffset) * 0.1 + sin(f_targetIndex + trigOffset));
        highp vec2 gridBoundTargetPosition = getGridPosition(targetPosition);
        highp vec2 edgeBoundPosition = vec2(gridBoundTargetPosition.x, gridBoundTargetPosition.y);

        highp float distanceToTarget = length(gridBoundUV - round(gridBoundTargetPosition)) + distance(gridBoundUV, edgeBoundPosition);

    	blueIntensity += length(GRID_CELL_SIZE / (distanceToTarget * 15.5)  / cellBoundUV) * GRID_CELL_SIZE;

    }


    highp vec3 col = vec3(smoothstep(0.2, 1.0, redIntensity + blueIntensity));

	col += redIntensity * vec3(0.0,1.0,0.0);
   	col += blueIntensity * vec3(0.0,0.0,1.0);

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