The changes are mostly subtle, keeping most of the enemies and power-ups the same while slightly changing the level layouts. The palette is more intense but not overbearing. Boss fights are livened up via different room geometry, and in one case, double-teaming. There are more enemies, most notably the animal kind (bats!). Unfortunately, enemies added via NinJax have a bug in that they immediately respawn when killed. This, combined with the fact that sometimes they spawn right next to Ryu (instead of at the edge of the screen like in the original game), makes a couple of levels very frustrating. You kill a bat and immediately get hit when it spawns again in the same place you just killed it. Argh!

There are a couple of other bugs with boss health; in the aforementioned double-team boss, both bosses have a full health bar that decrements, but you seem to win when their net health loss is 16 hits. It seems like you should have to kill both of them, not “one guy’s worth” between the two. For Jaquio at the end, his health REFILLS when you run across the room, a fact that made me reach for the save state. Putting the jump & slash power-up in the room with Jaquio feels cheap to me - I think it is overpowered against bosses in the original game as well. On the other hand, it is maddening to lose to him and go all the way back to 6-1. How about removing the jump & slash and having it send you back to the room right before the fight with Dad if you die?

All in all, this was a refreshing run through the old classic, even with the bugs.