This is bar none one of my favorite NES games. It's like a mix between a platformer and a point and click. You have to explore, find items and use them to solve puzzles around the forest and eventually the surrounding areas. You can hold a few items at a time so you might end up having to "come up with a place" to stash the items you don't need, resident evil zero style (but be wary of leaving out too many in the same area because due to hardware limitations they might actually disappear forever.)
I really like the UI and the effort put into the game, every single area of the game has some flavor text to it. The general goal of the game is to save your eggy friends who have each gotten into some trouble around the treehouses you live in, and eventually defeat the evil wizard who took your egg girlfriend. Overall it's a very technically impressivelly pulled off game for this era and this hardware. The most exploring you'll ever do in a NES game.