What are Synthetix trading fees?

As a crypto enthusiast, I'm curious about the cost associated with trading on Synthetix. Could you please elaborate on the Synthetix trading fees? Are they static or do they vary based on certain conditions? Do traders pay a flat fee or is it a percentage-based system? Additionally, are there any hidden costs or additional fees that traders should be aware of? Understanding the fees structure is crucial for making informed trading decisions on Synthetix, so I'd appreciate a detailed explanation.