When you drag the line gets longer based on how long you drag. This has an influence on your jump strength. Thinking about it do you use an hdpi monitor? Could be that this is broken with high resolutions.
The triangle is always the same length no matter what happens for me. I am playing on a MacBook Pro.
If you want to replay it for the gameplay that is what timed mode is made fo.
Interesting. Timed mode is disabled for me. The “Reset Progress” button is also disabled for me. I think the game always assume I am starting with zero progress or something? I am launching the game from the itch app.