I added the invasive species, because science classes in my schools study invasive species. This was straightforward. I added a collision, to delete grass if the invasive species touched it. This models an invasive species at choking out a native species. A minor struggle was to make the invasive species a bright color, so I could see it easily. I look forward to collaboration on this between Tech and Science at my school. I need help through collaboration, to tie this in to existing science curriculum. Fortunately my colleagues in our Science Department are looking forward to collaborating on this.