So I just watched a playthrough of the first boss and it was very cool. I appreciate you immediately subverting the player's expectation of being able to climb its legs, forcing them to ascend the tower. Anyway, one thing I thought about while watching the fight was the addition of destructible parts to the giant. The first boss is rotten and falling apart but it doesn't suffer any damage when the MC shoves the "gong pistons" into its week points three times over. It would be cool if small sections would crumble after the third impact, not only giving the player a sense of accomplishment but also clearly showing that they'll have to look elsewhere to inflict more damage. Finally, it would add weight to the gong pistons, making them feel like they could actually topple giants (like Kratos' Hit Stop design in God of War). Another thing which could be nice is when the player is climbing the tower and finds the brazier near the top. I'm sure most players will stop here to warm up so its a great opportunity for the giant to lash out and break the thin stone wall and topple the fire. This would add to the sense of urgency of the battle while also avoiding the player camping while completely protected from the breath attacks.