Circle to Rounded Rectangle Morph Transition

[ESGraphx]

Hello everyone! So on and off for the last couple of weeks, I've been trying to recreate my YouTube channel's "Subscribe" animation that was made by someone else for practice and to add in an updated logo. However, what would seem like the easiest part of it has actually been super frustrating for me: the circle to rectangle morph

I do have a decent amount of AE experience already but can't seem to figure this one out. I've tried a ton of tutorials and done the copy paste bezier path technique, messed with mask interpolation, changed first vertex, etc but I feel like I'm overcomplicating things. Anyone know an easier way to do this? Or how to just in general? I attached how it should look and how it looks with my version. Thank you!

[Rick Gerard]

Instead of animating a bezier path, create a rectangle, animate its size from 400, 400, to 800, 400, and animate its roundness from 200 to 25.

Adjust the speed curves of the animations using the Graph Editor to control the timing.

The Red YouTube logo also has a little Effects/Bulge applied to it. 

[ESGraphx]

Oh my god, I feel so stupid😅 This was the first thing I tried WEEKS ago, since it obviously makes the most sense, but for some reason the rectangle never turned into a full circle. Turns out I just had to click off and drag the attribute number again to complete the circle, I don't know why it wasn't working before but thank you so much!

[ESGraphx]

Actually I think its because I tried doing it as a circle to rectangle, not a square, which has all equal sides so the roundness is even👍🏻