first build attempt

shaders/graticule.frag

@@ -0,0 +1,17 @@
+/*
+ * MIT License
+ * Author: Mark Allyn
+ *
+ * graticule.frag — single-colour fragment shader shared by the
+ * incandescent bearing graticule and the yellow cursor overlay.
+ * The colour (and alpha) is set via a uniform so one shader serves both.
+ */
+#version 330 core
+
+out vec4 fragColor;
+
+uniform vec4 u_color;   // RGBA; use alpha < 1 for soft edges if needed
+
+void main() {
+    fragColor = u_color;
+}