I've been revisiting this game lately and will be attempting to improve my personal best score to around 650,000 points soon (current PB is 630k).
Like many Shinobi players, I've always struggled with Mandara boss and either lost a life (which is bad if you're going to be point pressing with your spare lives) or had to burn my ninja magic (and subsequent 5,000 point bonus) to "get inside" the statue sprite to start the bouncing luck game.
Using this technique that I found while studying BenShinobi's French guide, you can always make it through the bouncing by holding the down and left diagonal. I left the input view on in MAME so everyone could see what I did.
At this time, Pete Hahn - Retro Gaming has 1,953 views for Shinobi spread across 1 video. His channel published less than an hour of Shinobi content, less than 0.02% of the total video content that Pete Hahn - Retro Gaming has uploaded to YouTube.