Simple step-through debugging
Simply write/paste your code and press run. A full trace of your code's behavior will be made available to you, like; variables, functions, classes, and all lines that were touched. See which variables were assigned, how and when they were modified.
Step through the program by going forwards and backwards. Feel like you missed a step? Just go back some steps, no need to stop and fully re-run the code. Or just skip all the intermediate steps by immediately stepping to the end to view the output.