Basic info: Cave Story is a free game developed by Daisuke "Pixel" Amaya. It is a 2D side scrolling RPG shooter (like megaman or metroid) and is heavily pixel based. Your adventure starts out a mystery and you find out all what is happening around you the more you progress in the game. There are multiple weapons to choose from such as a standard pistol to missile launchers to a duck gun that shoots ducks. All weapons advance the more energy crystals you get (3 being maximum level) and simmer down in levels the more you are hurt. There are multiple different endings to the game, some depending on what actions you choose to do in certain parts of the game.


Gameplay:


link to website: http://cavestory.org/downloads_game.php

Get the main download first then install the English translation.
(There is also a deluxe version of Cave Story available for steam here but it costs money) store.steampowered.com/app/200900/

I would very much enjoy seeing Pewds' reaction to the game and if anything to see Cry play it.

I hope I did good for my first suggestion