system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why is it that some pens will work when you scribble, but stop working the moment you try and write letters?
gpt
The tip of the pen are sensitive to the pressure, and whenever it malfunctions, that's usually the case.

And it is not just about how hard you press down your pen, but the direction of your writing relative to your dominant hand.

If you write with left hand and the sentence directions are headed towards right, your hand will apply more pressure to the pen, making it more prone to malfunction.

When you scribble you're most likely Not applying the same amount of force (ie. lighter force than usual) on the tip of the pen, so it looks like it is working properly.