This is supposedly an old NES game the Oliver Twins never finished, but released a couple of years ago after a campaign to get it completed. It’s a pretty simple side-scrolling platform game, which doesn’t really stand out in any way (aside from being incredibly easy!) but does look and sound good for a NES title.
There are only 15 or so levels, and they’re not especially long. Most of them have a powerup which you can collect which makes you both move twice as fast, and become invincible for a short time, making them even shorter. Mind you, I died three times and twice were because I was under the influence of said powerup and I ran into lava (which still kills you).
It seems you can extend the game by collecting all the stars in each level, but this doesn’t appear to actually do anything (although you get an extra life for every 100) and none are actually tricky to reach, so by halfway through the game I stopped bothering.