Look at these important things that I circled:

I added a save/load feature! The main reason I did this is so that I can more easily develop and balance levels, but it also has a secondary use. I didn’t encrypt the save file, so you can edit it all you want. The names and everything is pretty straightforward. To access it, go to C\users\<username>\appdata\local\some_tower_defense_game\save1.ini
If you can’t find the appdata folder, go to control panel, find folder options, and enable viewing hidden folders. I also shaded out all of the towers that you can’t buy, and I did some bug and graphical fixes.