I think you should have found 15.Nh4. Attacking on the kingside is a major theme in the Ruy Lopez for white, the plan of Nh4 / f4 should be foremost in your mind.  c3 is anti-positional as your c2,d3,e4 pawn chain tells you to attack on the other wing, not to mention black's mass of pieces on the queenside suggesting that it is the kingside where you have the advantage.

Controlling f5 is a common motif in the Ruy, with the queen knight going b1-d2-f1-g3-f5, while the king knight can go g1-f3-h4-f5.  Qd1-e1-h4 is another idea to get the queen involved in the kingside attack.

Check out Melik's last video on becoming an expert for some thematic ideas here.  You will get a lot out of it I think.

Good luck!

solllevy10 I thought that if Black exchanged on d5 (after 16.c4) I'd be better off even with doubled-pawns (often not a problem with doubled-center pawns). Now I really don't know what the *@&#^%$?!! I was thinking but I'm pretty sure the RL is over my head from the White side of the bd.

Maybe I'll learn something from chess.com and Houdini (hopefully), but at this point I've learned not to play the RL as white!

perhaps you can expound on the 16.c4?! idea. you were probably anticipating 16...c6, and the only probable reason i can think of why 16.c4?! is not scared of 16...c6 is due to 17.Bxf7.

Just a name I use for all challenge games, I get tired of "Lets Play!" all the time

What's the "Redwood Empire Invitational Tnmt"?