Mr.X Nightmare is interesting in concept. Essentially a horde mode where the player selects their character, fights through waves of enemies on different stages with their own unique obstacles, and stacks buffs and bonuses at the end of each round to keep in competition with the climbing difficulties of each subsequent horde. It's alright. A perfectly fine Saturday morning distraction. Get a cup of coffee, turn on your favorite podcast, and shut your brain off for an hour or two.
But I also would caution against expecting anything more than that. There's not a ton of depth here. What you see is what you get, and outside of timed challenges (which appear to be set waves and bonuses rather than the procedural base mode), there's not a whole lot to it.
The real bonus to Mr.X Nightmare is the additional characters that unlock for Streets of Rage 4's story mode. Each one is fantastic and it really adds a lot to the game. I found the lineup of DLC characters to generally be more enjoyable than the main cast (outside of Cherry, who I really like playing as), and they're worth the price of admission alone. Which isn't that much, either. You can find the physical edition of Streets 4 with Mr.X Nightmare included for about three bucks more than the base game, on average, and at that point there's really no reason not to splurge for it. Definitely pick up this version if you've had your eyes on Streets of Rage 4.
But I also would caution against expecting anything more than that. There's not a ton of depth here. What you see is what you get, and outside of timed challenges (which appear to be set waves and bonuses rather than the procedural base mode), there's not a whole lot to it.
The real bonus to Mr.X Nightmare is the additional characters that unlock for Streets of Rage 4's story mode. Each one is fantastic and it really adds a lot to the game. I found the lineup of DLC characters to generally be more enjoyable than the main cast (outside of Cherry, who I really like playing as), and they're worth the price of admission alone. Which isn't that much, either. You can find the physical edition of Streets 4 with Mr.X Nightmare included for about three bucks more than the base game, on average, and at that point there's really no reason not to splurge for it. Definitely pick up this version if you've had your eyes on Streets of Rage 4.