Riddle me this: a ringtone for Archimedes' heart?

I stand in a wall, yet I’m never quite still, I let in the sun, yet I bend to your will. I frame the world, though I hold no brush, I can open to chatter, or silently hush. What am I?

I gloop when you are quiet, I set when you thwack. I ooze from your palm, I punch you right back. I am easy to make, I am half of two to make one. I am hard when you go fast; if I am soft, you will fall. I bend all the rules if you look how I look.

The answer to this riddle is a piece of cake.

with a shell of gold, I hold riches untold, but once you see me, there’s nothing left for thee. chased for ages, yet never found, not even sure who spoke the lie. for rainbows end up far too high, and no leprechaun’s been seen, outside of Hollywood and meme.