+/* if pixels is 0, it defaults to fb_pixels */
+void swap_buffers(void *pixels);
+
+/* call each frame to get 3D viewing spherical coordinates */
+void mouse_orbit_update(float *theta, float *phi, float *dist);
+
+void draw_mouse_pointer(uint16_t *fb);
+
+/* compiled sprites available */
+void cs_font(void *fb, int x, int y, int idx);
+
+/* helper to print text with cs_font */
+void cs_puts(void *fb, int x, int y, const char *str);
+