@TON-RIJNAARD You need to select the board based on the bootloader you have flashed. Complile the code in Arduino and try burning the hex file using a programmer (USBasp, AVRISP, etc..) if are facing issues with Arduino.
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.
Do you have interest to try OH2 together with MySensors Ethernet Gateway to get working?
I do not have enough force to push developers to make this happen. At the moment there is some problem on this, because full control is not possible. I think that MySensors Serial Gateway is working with OH2, but I don't like to use it. I like to connect my devices into LAN not cabling via old fashioned way using serial wires.
Added sketch, which also supports an additional mini PIR sensor. It's what I needed, you can comment to #define out.
Also changed the regulator to a smaller one, which supplies up to 100 milli Amp, which is plenty enough. That way I can keep the circuit smaller on the PCB. Which allows me to create a smaller housing.
I buy them on Aliexpress:
If you apply hot air it is easy to take off the white "double sided tape" and the plastic.