Arduino "Fireflies" Lamp with Light Detector & Sleep Mode

Board: 
Robotdyn Arduino Pro Mini 3.3V, 8MHz
(Attention! The wrong pinout by the manufacturer in the *pdf doc, use UNO's labels! pin 11 is PWM, not 12!)
 
Connection:
GND |-----< 9k1 >----- (A3) ------< LDR >-----> VCC 3.3V
GND |-----< cathode LED anode >-----< 240R >-----> to PWM pin (3, 5, 6, 9, 10, 11)

Energy-saving:
- Remove Power LED from the board
- Remove DC regulator

Code: https://github.com/ardubit/fireflies