diff --git a/tests/pg_test/pg_test.c b/tests/pg_test/pg_test.c
new file mode 100644
index 0000000..c028d5f
--- /dev/null
+++ b/tests/pg_test/pg_test.c
@@ -0,0 +1,124 @@
+#define STB_DEFINE
+#include "stb.h"
+#define STB_PG_IMPLEMENTATION
+#include "stb_pg.h"
+#define STB_IMAGE_IMPLEMENTATION
+#include "stb_image.h"
+#define STB_IMAGE_WRITE_IMPLEMENTATION
+#include "stb_image_write.h"
+
+static float *hf;
+static int hf_width = 10001;
+static int hf_height = 10001;
+
+static float get_height(float x, float y)
+{
+   float h00,h01,h10,h11,h0,h1;
+   int ix,iy;
+   if (x < 0) x = 0;
+   if (x > hf_width-1) x = (float) hf_width-1;
+   if (y < 0) y = 0;
+   if (y > hf_height-1) y = (float) hf_height-1;
+   ix = (int) x; x -= ix;
+   iy = (int) y; y -= iy;
+   h00 = hf[(iy+0)*hf_height+(ix+0)];
+   h10 = hf[(iy+0)*hf_height+(ix+1)];
+   h01 = hf[(iy+1)*hf_height+(ix+0)];
+   h11 = hf[(iy+1)*hf_height+(ix+1)];
+   h0 = stb_lerp(y, h00, h01);
+   h1 = stb_lerp(y, h10, h11);
+   return stb_lerp(x, h0, h1);
+}
+
+void stbpg_tick(float dt)
+{
+   int i=0,j=0;
+   int step = 1;
+
+   glUseProgram(0);
+
+   glClearColor(0.6f,0.7f,1.0f,1.0f);
+   glClearDepth(1.0f);
+   glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
+
+   glDepthFunc(GL_LESS);
+   glEnable(GL_DEPTH_TEST);
+#if 1
+   glEnable(GL_CULL_FACE);
+
+   glMatrixMode(GL_PROJECTION);
+   glLoadIdentity();
+   gluPerspective(60.0, 1920/1080.0f, 0.02f, 8000.0f);
+   //glOrtho(-8,8,-6,6, -100, 100);
+
+   glMatrixMode(GL_MODELVIEW);
+   glLoadIdentity();
+   glRotatef(-90, 1,0,0); // z-up
+
+   {
+      float x,y;
+      stbpg_get_mouselook(&x,&y);
+      glRotatef(-y, 1,0,0);
+      glRotatef(-x, 0,0,1);
+   }
+
+   {
+      static float cam_x = 1000;
+      static float cam_y = 1000;
+      static float cam_z = 700;
+      float x=0,y=0;
+      stbpg_get_keymove(&x,&y);
+      cam_x += x*dt*5.0f;
+      cam_y += y*dt*5.0f;
+      glTranslatef(-cam_x, -cam_y, -cam_z);
+      if (cam_x >= 0 && cam_x < hf_width && cam_y >= 0 && cam_y < hf_height)
+         cam_z = get_height(cam_x, cam_y) + 1.65f; // average eye height in meters
+   }
+
+   for (j=501; j+1 < 1500+0*hf_height; j += step) {
+      glBegin(GL_QUAD_STRIP);
+      for (i=501; i < 1500+0*hf_width; i += step) {
+         static int flip=0;
+         if (flip)
+            glColor3f(0.5,0.5,0.5);
+         else
+            glColor3f(0.4f,0.4f,0.4f);
+         flip = !flip;
+         glVertex3f((float) i, (float) j+step,hf[(j+step)*hf_width+i]);
+         glVertex3f((float) i, (float) j   ,hf[  j    *hf_width+i]);
+      }
+      glEnd();
+   }
+
+   glBegin(GL_LINES);
+      glColor3f(1,0,0); glVertex3f(10,0,0); glVertex3f(0,0,0);
+      glColor3f(0,1,0); glVertex3f(0,10,0); glVertex3f(0,0,0);
+      glColor3f(0,0,1); glVertex3f(0,0,10); glVertex3f(0,0,0);
+   glEnd();
+#endif
+}
+
+void stbpg_main(int argc, char **argv)
+{
+   int i,j;
+
+   #if 0
+   int w,h,c;
+   unsigned short *data = stbi_load_16("c:/x/ned_1m/test2.png", &w, &h, &c, 1);
+   stb_filewrite("c:/x/ned_1m/x73_y428_10012_10012.bin", data, w*h*2);
+   #else
+   unsigned short *data = stb_file("c:/x/ned_1m/x73_y428_10012_10012.bin", NULL);
+   int w=10012, h = 10012;
+   #endif
+
+   hf = malloc(hf_width * hf_height * 4);
+   for (j=0; j < hf_height; ++j)
+      for (i=0; i < hf_width; ++i)
+         hf[j*hf_width+i] = data[j*w+i] / 32.0f;
+
+   stbpg_gl_compat_version(1,1);   
+   stbpg_windowed("terrain_edit", 1920, 1080);
+   stbpg_run();
+
+   return;
+}