Ok, finally it's solved. I installed everything from scratch. Then installed your sandeep lib from your github. And finally added the LEDs and Buttons to the variants.h. That compiled successfully. And my problem was that the sensor is sleeping and I couldn'T get a heartbeat answered.
So everything is clear and now testing...
I think these look very interesting to do with small children may be able to stimulate their curiosity, the current video games are too much influence on children, occasionally the family together to do their own small games is a new experience.
@waspie Apologies for resurrecting this thread after two years. I have quite a few NRF51822 boards with me. I would like to put it to use. Can you please share your code as following these links did not help me compile the sketch. Too many errors. Thanks in advance.