+ Zborder, /* special code to indicate border */
+ Zplayer, /* special code to indicate player */
+
+ Zbug, /* internal bug explosion */
+ Ztank, /* internal tank/alien/bomb explosion */
+ Zeater, /* internal eater explosion */
+ Zdynamite, /* internal dynamite explosion */
+ Zboom, /* explosion */
+
+ Xchain, /* chain explosion; transition to Zboom */
+ Xboom_bug, /* bug explosion; transition to Zbug */
+ Xboom_tank, /* tank/alien/bomb explosion; transition to Ztank */
+ Xboom_android, /* android explosion; transition to Xboom_2 */
+ Xboom_1, /* tile explosion; transition to Xboom_2 */
+ Xboom_2, /* transition to boom[] */
+
+ Xblank,