Ninja Spirit began life as an arcade game and since then has received many ports, including a Game Boy version and this version. It would be a stock platform game but for the ability to have up to two 'spirits' which behave like the options from Gradius.
This run is played on Arcade mode, where the character dies in one hit and bosses are stronger; the other available mode (appropriately titled PCE mode) allows taking more than one hit and is overall easier. People familiar with the game should be able to appreciate the difference, as Arcade mode is extremely challenging.