Problematic shader code

night.fragment.glsl

#ifdef GL_ES
precision mediump float;
#endif

varying vec4 v_color;
varying vec2 v_texCoords;
uniform sampler2D u_texture;

uniform vec3 u_playerPosition;
uniform float u_playerLightRangeScaled;

void main()
{
	vec4 tex = v_color * texture2D(u_texture, v_texCoords);
	float texLight = (tex.r + tex.g + tex.b) / 3.0;

	float d = distance(gl_FragCoord, u_playerPosition.xy);

	// Make things dark and blueish
	gl_FragColor = vec4(texLight/5.0, texLight/5.0, texLight/3.0, tex.a);

	// If we're within range of the player, light up a bit, based on distance
	if (d < u_playerLightRangeScaled) {
		float fadeAmount = d / u_playerLightRangeScaled;
		gl_FragColor = (tex * (1.0 - fadeAmount)) + (gl_FragColor * fadeAmount);
	}
}

On my desktop, this works fine, but on my tablet which uses OpenGL ES 3.0, it doesn't.

The error I'm getting is: No matching overload for function 'distance' found but the docs say that distance() is compatible with all versions. I don't think it should be using the genDType version, as u_playerPosition is a vec3.
Any ideas?

Argh! It was because I used gl_FragCoord rather than gl_FragCoord.xy on line 17. Why did this not throw an error when I first wrote it? Argh.