precision mediump float;

uniform vec4 color;

varying vec3 vertexNormal;

void main() {
	vec3 normal = normalize(vertexNormal);
	float lambert = max(0.0, -normal.y);
	float rim = 1.0 - lambert;
	rim *= rim * rim;
	gl_FragColor = rim + (0.4 + 0.4 * lambert) * color;
}