Arduino.h: No such file or directory on Mac

Hi,
Really appreciate it if you can help me on this issue. I am new to Arduino. I just got my M2 board a couple of days ago and followed the guide
http://docs.macchina.cc/m2/getting-started/arduino.html
However, I cannot get my example Blink running, it kept reporting
"sketch/Blink.ino.cpp:1:21: fatal error: Arduino.h: No such file or directory
** #include <Arduino.h>**
** ^**
compilation terminated.
exit status 1
Error compiling for board Macchina M2."

My environment:
Mac OS: High Sierra, version 10.13.3
Arduino IDE 1.8.4
Board:“Macchina M2"
Port:”/dev/cu.usbmodem14111"

Thanks!

did you figure this out yet?

Hello! It should be in the Arduino.app package. When you open it in Finder there should be more files visible.

From terminal it should be in:
/bin/arduino-1.8.5/hardware/arduino/avr/cores/arduino

Or you can pull it from GitHub and direct it to a folder on your Mac

https://github.com/arduino/Arduino/tree/master/hardware/arduino/avr/cores/arduino