Preview rotation follows device

data/blit.vert

@@ -5,10 +5,12 @@ precision mediump float;
 attribute vec2 vert;
 attribute vec2 tex_coord;
 
+uniform mat3 transform;
+
 varying vec2 uv;
 
 void main() {
 	uv = tex_coord;
 
-	gl_Position = vec4(vert, 0, 1);
+	gl_Position = vec4(transform * vec3(vert, 1), 1);
 }