Hi, I stumbled upon old good https://pyalgoviz.appspot.com/ I wonder what are options to do it solely in browser: - skulpt? - brython? do they support `sys.settrace` functionality -- maybe with some js under-the-hood? -- Jurgis Pralgauskis tel: 8-616 77613; Don't worry, be happy and make things better ;) https://galvosukykla.wordpress.com/