I always thought it was hilariously similar to how to old NES zapper worked - the sensor was in the gun, it decided what you ‘hit’ based on what the sensor saw when the tv flashed. I think it was an early instance of me recognizing an engineering ‘hack’ - instead of the target reporting whether it had been hit, it was the gun reporting whether it thought it had hit the target.
Eh, it's just to force you not to use paper tickets and clog the machines. If you want to pay with cash, you're supposed to buy an Oyster card (£5) and top it up at the machine or most convenience shops across London.
So just give or take 35 million people, with Taiwan being integral to the world's chip manufacturing industry, and HK conquest violating the handover treaty. That's far from nothing.