Put a good amount of time into the UI. Feedback is appreciated!
Sorry for cramming the two windows together, but I wanted to show it side-by-side(The UI elements wouldn’t be touching on a real screen!).
https://gfycat.com/MinorBowedCrocodile
Edit: The Video I tried uploading didn’t work, so the Tweet will have to do, sorry.
Edit 2: No sound on Gyfcat, but it’s better than a Twitter link.
This is the smoothest trading system I’ve seen on Roblox so far. I like the interactions because they are intuitive and the UI is well made. I also think it’s super cool that you have to dual-authenticate the trade to complete it (i.e. click Confirm then click Accept). Nice work! 
Idea: When you click the same object multiple times, allow the trading window to put a number in the corner instead. So when you click the same thing three times it only occupies one slot in your trade. This will allow for larger-scale trading and more opportunity for players to get rid of duplicates.
awesome trading system bro love the animations
Your UI never ceases to amaze me. Animations on point 
Aye aye, let me have that.
Now that, looks nice. I love how smooth it looks side-by-side. I’ve seen live trading systems but they aren’t as immediate and don’t normally have transitions like this. Very nice work. I also dig your UI design - compact, easy on the eyes, vibrant, appealing.