Refactor into more modular architecture

asteroids.h

@@ -0,0 +1,27 @@
+#ifndef ASTEROIDS_H
+#define ASTEROIDS_H
+
+#include "physics.h"
+
+typedef void (*asteroids_cb_t)();
+
+typedef enum {
+	ASTEROID_SMALL,
+	ASTEROID_MEDIUM,
+	ASTEROID_LARGE,
+	ASTEROID_HUGE,
+} asteroid_size_t;
+
+typedef struct {
+	float probability;
+	asteroid_size_t size;
+} asteroid_size_dist_entry_t;
+
+void asteroids_clear();
+void asteroids_on_clear(asteroids_cb_t cb);
+
+void asteroids_add(const asteroid_size_dist_entry_t *dist);
+void asteroids_hit(unsigned shot, unsigned asteroid, physics_sep_t sep);
+bool asteroids_check(unsigned id);
+
+#endif