[marketforlemmas]

To be a little more clear about the diamond and circle...

LASSO is a diamond because it represents the constraint that w_1 + w_2 <= 1. The region of (w_1,w_2) that satisfy that inequality is a square.

Ridge is a circle because it represents the constraint that w_1^2 + w_2^2 <= 1. The region of (w_1,w_2) that satisfy that inequality is a circle.

[achompas]

Agh I forgot to mention this! Thank you, I'll add a note to my post.

[yelnatz]

This is the kind of reasoning I was looking for. Thanks!

[achompas]

Glad you got an answer. :)