Short-Term Crypto are Taxed by Gross or Net?

Is short-term crypto one of those things where you can pay tax even if your net gains are zero?

 

Example:

Event 1: Sell BTC for profit of $50,000 

 

Event 2: Sell BTC for loss of $100,000

 

Event 3: Sell BTC for profit of $50,000

 

Do you pay taxes on $0? or on $100,000?

 

Does it matter if you are professional or casual trader?

I ask because I know with gambling winnings, it does depend whether you are a professional gambler or amateur. For example, if you are an amateur, you can have a net gambling winnings of zero and still owe a tax bill because it's taxed differently. I was wondering if trading is the same?