SmartCard / Metrocard

Prepaid card has now become the indispensable tool in city life. It can help people quickly through the transportation charging set, parking lot, etc. and let the busy life more convenient.
But people always forgot how much remains when they use cards and were blocked outside because of insufficient balance, missed the transports and delayed the precious time.
Smartcard with a solar photoelectric plate built in it can show how much remains when you need to know. When you take out Smartcard from your wallet, the solar photoelectric plate of Smartcard can absorb light and thus can show the balance instantly and let your life more convenient.