Super tux is a 2d sidescrolling platformer with marioesque tones: I wrote a simple script to install it and add it to the ports menu just in case anyone is interested. create a shell script called supertux.sh in /home/pi/RetroPie-Setup/scriptmodules/ports and copy the content below into the script. you should then be able to install it from the experimental menu of the setup script.

#!/usr/bin/env bash

# This file is part of The RetroPie Project
# 
# The RetroPie Project is the legal property of its developers, whose names are
# too numerous to list here. Please refer to the COPYRIGHT.md file distributed with this source.
# 
# See the LICENSE.md file at the top-level directory of this distribution and 
# at https://raw.githubusercontent.com/RetroPie/RetroPie-Setup/master/LICENSE.md
#

rp_module_id="supertux"
rp_module_desc="SuperTux 2d scrolling platform"
rp_module_menus="4+"

function install_supertux() {
    aptInstall supertux
}

function configure_supertux() {
    cat > "$romdir/ports/SuperTux.sh" << _EOF_
#!/bin/bash
supertux
_EOF_

    chmod +x "$romdir/ports/SuperTux.sh"
    chown $user:$user "$romdir/ports/SuperTux.sh"

    setESSystem 'Ports' 'ports' '~/RetroPie/roms/ports' '.sh .SH' '%ROM%' 'pc' 'ports' 
}