Pass vertices through buffer instead of hard-coding

vert.glsl

@@ -1,20 +1,11 @@
 #version 450
 
-vec2 positions[3] = vec2[](
-	vec2(0.0, -0.5),
-	vec2(0.5, 0.5),
-	vec2(-0.5, 0.5)
-);
-
-vec3 colours[3] = vec3[](
-	vec3(1.0, 0.0, 0.0),
-	vec3(0.0, 1.0, 0.0),
-	vec3(0.0, 0.0, 1.0)
-);
+layout(location = 0) in vec2 position;
+layout(location = 1) in vec3 colour;
 
 layout(location = 0) out vec3 frag_colour;
 
 void main() {
-	gl_Position = vec4(positions[gl_VertexIndex], 0.0, 1.0);
-	frag_colour = colours[gl_VertexIndex];
+	gl_Position = vec4(position, 0.0, 1.0);
+	frag_colour = colour;
 }