Create RNG module

game.c

@@ -2,12 +2,11 @@
 
 #include "input.h"
 #include "renderer.h"
+#include "rng.h"
 
 #include <assert.h>
 #include <linux/input-event-codes.h>
-#include <stdlib.h>
 #include <string.h>
-#include <sys/time.h>
 
 #define FIRE_MEAN -0.15
 #define FIRE_JITTER 0.01
@@ -204,11 +203,6 @@ static void remove_entity(unsigned id)
 	--entity_count;
 }
 
-static float rand_plusminus()
-{
-	return 2.0f * ((float)rand() / RAND_MAX - 0.5f);
-}
-
 static void ship_update()
 {
 	entity_t *ship = entities + ship_entity_id;
@@ -221,7 +215,7 @@ static void ship_update()
 
 	shape_t *fire = shapes + fire_shape_id;
 	fire->visible = input.fwd != 0;
-	fire->verts[0].y = FIRE_MEAN + FIRE_JITTER * rand_plusminus();
+	fire->verts[0].y = FIRE_MEAN + FIRE_JITTER * rng_plusminus();
 }
 
 void game_init(float _aspect)
@@ -230,10 +224,6 @@ void game_init(float _aspect)
 	input_on_release(key_release_callback);
 	input_on_repeat(key_repeat_callback);
 
-	struct timeval tv;
-	gettimeofday(&tv, NULL);
-	srand(tv.tv_usec);
-
 	aspect = _aspect;
 	quit = false;