Algodoo

I made this. As of after part 3, 19 marbles have been eliminated: Balloon, Brown, Dark Brown, Dark Pink, Goldenrod, Grey, Lavender, Magenta, Night Sky, Orchid, Rope, Silver, Sky, Stone, Teal, Tracer Red, Tracer Yellow, Violet, and Wood. The last 3 marbles to reach the end of this little course rejoin! This will mean that there will be 51 marbles in Part 4.