extern float shipdx,shipdy; // Change in X position per tick.
extern float screendx, screendy;
extern float xscroll, yscroll;
-extern float gamerate; // this controls the speed of everything that moves.
+extern float framelen; // this controls the speed of everything that moves.
extern float yscroll;
extern float scrollvel;
extern int nships,score,initticks,ticks_since_last, last_ticks;
extern int gameover;
extern int maneuver;
-extern int sound_flag, music_flag;
-extern int tail_plume; // display big engine at the back?
-extern int friction; // should there be friction?
extern float fadetimer, faderate;
extern int pausedown, paused;