> With a modern context, I'm not sure where I would even start. I'm proficient with a bunch of programming languages, none of them seem as accessible as the BASIC code above.
Core Tcl (i.e., that portion which a child would be exploring in his/her first introductions to programming) is very close to BASIC in accessibility. Core Tcl has very little syntax overall. Compare the Tcl/Tk code above to draw on a Tk canvas to the BASIC code for the same. There is nearly a 1:1 correspondence. And Tcl/Tk also gives the added advantage that when the children gain a bit of proficiency, then can also easily create GUI's for their code snippets and apps. The GUI's they create may not be beautiful GUI's, but they would be "their GUI's" that they created with their own efforts.
Core Tcl (i.e., that portion which a child would be exploring in his/her first introductions to programming) is very close to BASIC in accessibility. Core Tcl has very little syntax overall. Compare the Tcl/Tk code above to draw on a Tk canvas to the BASIC code for the same. There is nearly a 1:1 correspondence. And Tcl/Tk also gives the added advantage that when the children gain a bit of proficiency, then can also easily create GUI's for their code snippets and apps. The GUI's they create may not be beautiful GUI's, but they would be "their GUI's" that they created with their own efforts.