GotoJSE is a retro styled version of BASIC, but with modern techniques, and a slant towards making 2D retro styled Games.
If you've ever used BlitzBASIC, BlitzMAX, SmileBASIC or other modern forms of BASIC, then you should be quite comfortable with the syntax of GotoJSE.
GotoJSE works entirely inside the browser, and no external files are needed, making this language great for examples and quick games.

(c) Nintendo
Don't expect to be making anything "Super" powerful using GotoJSE
GotoJSE is stable enough to make fun project with, and is powerful enough to create some interesting games in.
But you won't be making the next Fortnite with it!
It's mostly meant for making retro 2D games.
Everything you do in GotoJSE will be saved to your browser's cookies.
But cookies are not 100% foolproof, and you shouldn't rely on things always being stored forever.

You should frequently make use of the "Export Project Library" button.
I tend to use this at the end of each day, so that I have a collection of daily backups.
Every Export includes a date stamp on the filename, so you should always be able to find your most recent backup.
If you ever need to, you can upload this to your browser with the "Import Project Library" button, and all of your previous projects will reappear.
You can even copy the file over to a different computer/browser, upload it there, and your projects will be retained.
GotoJSE was originally created as a "Scripting Engine", intended for the purpose of showing quick programming/logic examples, and sharing those inside a Forum.
Since its creation, it's been made moderately more capable and is now good enough for making a variety of games, but it's still limited by "What you can do inside the single code box".
The "One box" limit remains, so file access isn't really workable, nor are external sounds, images, tilemaps and quite a bit more.
Everything must be achievable inside the single code box.
This is a fairly hefty limit, but .. it's workable! You just need to be creative :D
GotoJSE is an Interpreted language, though great pains have been made to make it run as fast as it possibly can.
Though it "could" potentially be compiled, there are a number of "Javascript Security" issues that make it not 100% foolproof on different browser/system combinations. What works on one device doesn't work on another.
A "Use the server to compile" method has been considered but then everything you ever code will need the server to be up and running 24/7, in order to compile things, and that's really not a good method to be locked into.
In general, if you find yourself needing more power than GotoJSE can cope with, then you're probably ready to move on to either Raw Javascript coding, or any number of other more powerful languages.
GotoJSE has been "good enough" for me to create over 100 AGameAWeek games.