Differences from JavaScript

Your code runs as Scratch blocks, so it follows Scratch's rules. Here's what to keep in mind.

Topic	What happens
break, continue, switch	Not supported. Use a flag in the loop condition, or return from a function.
Variable values	Kept between runs (green flag clicks). Reset them in whenFlag.
Variables inside functions	Become sprite variables, so they aren't safe across recursion.
Value-returning calls	At most one per statement. Split f(a) + f(b) into two variables. Loop and waitUntil conditions may call functions.
== / ===	Scratch equality: compares numbers numerically, text case-insensitively ("A" === "a" is true).
%	Result takes the sign of the divisor (-1 % 3 is 2).
sin, cos, ...	Use degrees.
Functions	Belong to their sprite. Share code through src/lib/ or the engine, which copy functions into each sprite that uses them. To trigger code in another sprite, use broadcast.
Objects	State objects ({ score: 0 }) and classes. Objects are created when the project is built: make them with new at the top of a file, and use clones when you need many at runtime.
me.visible	Can be set but not read (Scratch has no block for it). Keep it in a variable, or use Camera.onScreen.
Sprite positions	Scratch keeps sprites on stage, so a sprite can't move fully off screen. Hide it instead (Camera.place does this).
Lists	Hold numbers and text. No nested arrays.
Timing	Like Scratch, loops yield once per frame unless the function is marked /** @warp */.