Debugging paper circuits by soldering

I made a Halloween card previously using copper wire and paper circuits. Couple of day passed and since the transparent tape does not stick well, the joints become loose and several LEDs don't light any more or become flickery. 

So in this week's class, we learned to use soldering to fix this problem. With a soldering gun and some filler metal, we could melt the metal to connect the LED and the copper wire well.