system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How come sometimes my finger smoothly glides over the surface of my phone screen, but sometimes it drags and leaves a streak even if I just washed?
gpt
There are several factors that can affect how much resistance you have while moving your finger across your screen. For one, the harder you are pressing your finger down, the more friction there will be between your finger and the screen. You may do this without realizing this. Secondly, different amounts of sweat and grease may be present either on your fingertips or on the phone screen itself. If your hands are warm/sweaty or if it's warm in the air, you may get a more greasy interface between your fingers and the screen.