draw shot ring focus point where shot will land

assets/fs/shaders/shot-ring.v.glsl

@@ -2,12 +2,13 @@
 uniform mat4 projection;
 uniform mat4 modelview;
 uniform float scale;
+uniform float width;
 
-/* pos.xyz is position, pos.w is offset */
+/* pos.xyz is position, pos.w is 0/1 for inner/outer ring */
 attribute vec4 pos;
 
 void main(void)
 {
-    vec3 pos3 = pos.xyz * (scale + pos.w);
+    vec3 pos3 = pos.xyz * (scale + width * pos.w);
     gl_Position = projection * modelview * vec4(pos3, 1);
 }