Only if you choose to sell the shares will you be taxed on the then realized gains. The rate will be like 40% but you can't be taxed on them until you sell them and turn them into cash. It would be impossible for them to tax you on unrealized gains at some predetermined rate having no idea what the value will be when you decide to actually sell them. Makes no sense and not how it works.
You aren't listening, you can't be taxed on capital gains that haven't been realized...as in SELLING the stock for CASH. Your other examples of gifts, prizes, etc. are all other tax laws NOT capital gains.