Blocks snap into each other to define the program that your @boardname@ will run. Blocks can be event (buttons, shake, ...) or need to be snapped into an event to run. The on-start event runs first.
for (let i = 0;i<5;++i) {}
if (true){}
let x = 0;
Math.randomRange(0,5);
"".compare("");
[0].push(0);