I can't use let instead of var to create my variables

CS Principles Coding and Debugging Help
1

Link to the project or level: https://studio.code.org/projects/gamelab/7YyS6cyOSpD5wFVWwsFm1VkAysMORyJu_HHPPEsLJf0/view
What I expect to happen: the let keyword to create a variable
What actually happens: let throws an Error ERROR: Line: 9: SyntaxError: Unexpected token (9:4)
and that’s on a line i didn’t even write let on.
What I’ve tried: I’ve tried searching up on the Internet if let was a working keyword and what was it used for. I realized that what i did was right and i did nothing wrong. I also went to a Javascript compiler and tried to use the let keyword and it worked perfectly fine.

2

The Javascript interpreter that App Lab uses is based on Javascript version ES5. That means no let, no const. Only var.