for loops we use two sentinel nodes with a backwards edge, and before each iteration, we check the condition and update loop variables.

  sentinel -> body -> sentinel (condition with backwards edge to first sentinel)

in the UI, this is just represented as another block, and depending on the varying types of loops you can either define a collection or the number of iterations

and specifically nested loops. if you're spinning up full runtime copies for each loop, you're gonna have a hard time