I've had exactly the same problem as scargill - fatal error: Arduino.h: No such file or directory
Solved it by changing:
#mighty_opt.build.core=arduino:arduino
mighty_opt.build.core=standard
mighty_opt.build.core=arduino:arduino
#mighty_opt.build.core=standard
Dear bperrybap/Bill,
It is really encouraging to read on a forum messages like "Hurray! Got it working!" XD
If it is not too much trouble please explain how you made it)