Why are Grease Pencil Strokes converted to thin Lines? I was working on a small test animation within the 2d animation, but somehow hit a hotkey that I couldn't seem to find and fix it.

The image below shows how it looks after the accidental hotkey input.
I had the same problem with the random hotkey, still don't know what it was.

On the top right corner of the viewport are four icons which change the Viewport Shading.

Select the second or third icon on the top right corner of the viewport to change Viewport Shading