In RECEIVE Mode:

• Green LEDs flash
• Waits for flag to be received by IR sensor
• If flag is received, switchs to SEND Mode
• If corrupted flag is received, flashes red once

In SEND Mode:

• Red LEDs flash
• Every 10 seconds, sends flag via IR LED
• After about 13 minutes, deletes flag from memory and switchs to RECEIVE Mode

Parts list:

• 3 red LEDs
• 3 green LEDs
• 1 IR LED
• 1 Attiny85
• Resistors for each LED: 100ohm for IR and Red, 68ohm for green
• IR sensor TSOP4838
• CR2032 Battery holder
• 3V CR2032 Battery

If you want more detailed instructions, add an issue on github or message @idont_party