#define TICK_INTERVAL 30
+
+static Uint32 next_time;
+
+Uint32 time_left(void)
+{
+ Uint32 now;
+
+ now = SDL_GetTicks();
+ if(next_time <= now)
+ return 0;
+ else
+ return next_time - now;
+}
+
+
+/* main game loop */
+
+ next_time = SDL_GetTicks() + TICK_INTERVAL;
+ while ( game_running ) {
+ update_game_state();
+ SDL_Delay(time_left());
+ next_time += TICK_INTERVAL;
+ }