-void update_log (struct World * world, char * text) {
-// Update log with new text to be appended.
- char * new_text;
- uint16_t len_old = strlen(world->log);
- uint16_t len_new = strlen(text);
- uint16_t len_whole = len_old + len_new + 1;
- new_text = calloc(len_whole, sizeof(char));
- memcpy(new_text, world->log, len_old);
- memcpy(new_text + len_old, text, len_new);
- free(world->log);
- world->log = new_text; }
+void save_game(struct World * world) {
+// Save game data to game file.
+ FILE * file = fopen("savefile", "w");
+ write_uint32_bigendian(world->seed, file);
+ write_uint32_bigendian(world->turn, file);
+ write_uint16_bigendian(world->player->pos.y, file);
+ write_uint16_bigendian(world->player->pos.x, file);
+ write_uint16_bigendian(world->monster->pos.y, file);
+ write_uint16_bigendian(world->monster->pos.x, file);
+ write_uint16_bigendian(world->monster->next->pos.y, file);
+ write_uint16_bigendian(world->monster->next->pos.x, file);
+ write_uint16_bigendian(world->monster->next->next->pos.y, file);
+ write_uint16_bigendian(world->monster->next->next->pos.x, file);
+ fclose(file); }
+
+char is_passable (struct Map * map, uint16_t y, uint16_t x) {
+// Check if coordinate on (or beyond) map is accessible to movement.
+ char passable = 0;
+ if (0 <= x && x < map->size.x && 0 <= y && y < map->size.y)
+ if ('.' == map->cells[y * map->size.x + x])
+ passable = 1;
+ return passable; }
+
+struct yx_uint16 mv_yx_in_dir (char d, struct yx_uint16 yx) {
+// Return yx coordinates one step to the direction d of yx.
+ if (d == NORTH) yx.y--;
+ else if (d == EAST) yx.x++;
+ else if (d == SOUTH) yx.y++;
+ else if (d == WEST) yx.x--;
+ return yx; }
+
+void move_monster (struct World * world, struct Monster * monster) {
+// Move monster in random direction, trigger fighting when hindered by player/monster.
+ char d = rrand(0, 0) % 5;
+ struct yx_uint16 t = mv_yx_in_dir (d, monster->pos);
+ if (yx_uint16_cmp (t, world->player->pos)) {
+ update_log (world, "\nThe monster hits you.");
+ return; }
+ char met_monster = 0;
+ struct Monster * other_monster;
+ for (other_monster = world->monster; other_monster != 0; other_monster = other_monster->next) {
+ if (other_monster == monster)
+ continue;
+ if (yx_uint16_cmp (t, other_monster->pos)) {
+ met_monster = 1;
+ break; } }
+ if (met_monster)
+ update_log (world, "\nMonster hits monster.");
+ else if (is_passable(world->map, t.y, t.x))
+ monster->pos = t; }