Extend player progress bar to end of window (Sonic theme)

The topic title might be difficult to understand. I'm referring to the orange line in the picture below:

Clicking to the middle of a song is difficult because the progress bar is invisible! Having the orange line extend to the right side of the page, but maybe grayed out, would make selecting the time much easier. This doesn't apply to the default theme, but it affects several of the other themes (including at least Sonic).

Clicking to the middle of a song is difficult because the progress bar is invisible! Having the orange line extend to the right side of the page, but maybe grayed out, would make selecting the time much easier. This doesn't apply to the default theme, but it affects several of the other themes (including at least Sonic).