Execution controls, speed, and step

Most beginners press Run repeatedly when they are confused. Code Lab gives you better tools than that.

What the main controls do

At the top of the workspace, Code Lab exposes these execution controls:

Run starts the current program
Pause freezes an active run so you can observe the current state
Resume continues from a paused state
Step executes one block at a time when you are working carefully
Stop ends the current run
0.5x / 1x / 2x change how fast execution moves

What changes on screen during a run

A healthy run usually gives at least one clue that execution really started:

Run changes into Pause
a Stop button appears
widgets begin updating
the log timeline gains new activity

If none of those things happen, slow down and recheck the workspace before clicking again.

When Step is most useful

Use Step when:

a template works, but your small edit changed the behavior
you want to understand the order of blocks more clearly
the output changes too quickly during a full-speed run

Step mode is not mainly about speed. It is about understanding sequence.

When speed controls help

Use the speed controls like this:

0.5x when you want to watch a process more carefully
1x for normal testing
2x only when you already trust the logic and want to move faster

If a learner says “the tool is too fast,” the best next move is usually slower speed or Pause + Step, not rebuilding the program from scratch.

A good debugging rhythm

When something looks wrong:

stop the current run
make one small change only
run again at normal or slower speed
pause if the behavior becomes hard to follow
use step mode to isolate where the logic changes

This rhythm keeps the workspace teachable.

Python readiness note

If you are using Python, the runtime may need to finish loading before Run is available.

If that happens:

wait for readiness instead of spamming the button
keep inspecting the blocks or template while the runtime loads
switch to JavaScript only if you intentionally want a different language path

Good learner habit

Think of the controls as a sequence:

Run to start
Pause to observe
Step to inspect
Stop to reset your thinking before the next attempt

That mindset makes Code Lab feel much less random.