Discovered by chance everycircuit on Android as Ooklets was asking Daddy Ook to do electronics with them.
I played around with everycircuit app, and it is very nice to experiment with voltages and the such without burning components out.
Really nice.
My first project was to get some LED’s working from a 14V power source (car in motion), and I subsequently discovered :
LED’s in serial is a no-no, because if one pops, then they all go dead. Try finding the dead one then 
From that I progressed to 10 LED’s in parallel, and a single 40Ohm resistor. Works nice, but if more than one LED pops, then you’ll lose the rest of the LED’s due to overvoltage.
Eventually I discovered that 10 LED’s in parallel, but each one with a 400Ohm resistor works the best. If one pops, the rest keep on working.
But now the question - why a 40Ohm resistor in the first design, but 10 400Ohm resistors in the second?
Interesting, nice to play with! No more burnt pieces of solder all over the place or the SO moaning about the lovely smell of burnt circuitry and things 
14V - because that is the charging voltage for a 12V battery. I decided to spec it for 14V and have equipment lasting longer than speccing it for 12V and getting burnt things on a regular basis.
