What's the Toughest Branch in Electronics?



What's the Toughest Branch in Electronics?

Examples:
Smps design (switchers for..everything!)
Audio design (power amplifiers, analogue filters)
RF design (radio transmitters, receivers, radar, cellphones)
Digital design (computers,microcontrollers,FPGA)

I'll guess this order of difficulty.
1) RF design
2) Smps design
3) Audio design
4) Digital design


D from BC
.