The key to success in Ninja Gaiden is simple. Once you have Jump and Slash, NEVER LOSE IT!!! Showed my brother how to navigate through stage 4 and kill the Kelbeross with the Jump and Slash technique, before it ever actually left its pedestal, negating the entire fight. He asked me to record it, and I ended up going from the beginning of 4-1 through the entirety of the level with the original Jump and Slash technique found in the Jungle (though technically I do pick up the double in 4-2). No deaths and the score stays current throughout. No tools were used to do this, it was just something I used to push myself to try as a kid. Gotta be good at something I guess :-)