Vengeful Guardian Moonrider is a solid, competent, and charming love letter to Shinobi with a bit of Mega Man X thrown in, from Brazilian devs Joymasher, who have had a long history of this sort of retro pastiche. The main character in Moonrider is a ninja cyborg with a sword, a jump kick, a running slash, and a wall jump which he uses to great skill doing the usual Mega Man ninja stuff across nearly a dozen swiftly paced levels. There is not a lot here that will surprise you, but the game remains markedly competent the whole way through, with good variety, solid design, fair balancing with midlevel health appropriate to the damage you are taking, and entertaining bosses. Since your main weapon is a sword slash and most of the bosses are rival mecha-ninjas, the bosses often end up feeling a bit like a fighting game at times, with you needing to read and react to uppercuts and charge attacks while stealing hits while the enemy recovers. Cannot say I am a fan of the story though, but there is very little of it.
Unfortunately as a competent, fun, short, replayable game, there is not a lot to say about it. It is solid and worth playing, paced quickly enough that it is a solid afternoon's play without overstaying its welcome. It probably will not dislodge any of your childhood classics but you absolutely will not regret the time spent with it.