ATtiny85 Traffic Stop Light - This program turns on (in order) the Red LED, waits for 5 seconds, then turns on the Green LED, waits for 5 seconds, then turns on the Yellow LED, waits for 2.5 seconds and repeats cycle.

ATtiny85_TrafficStopLight.ino

/* ATtiny85 Traffic Stop Light - Version 0.1.2 - 2020-02-15
 * Copyright (c) 2020 Matt Rude <matt@mattrude.com>
 * 
 * *********************************************************************************
 * 
 * This is a simple Traffic Stop Light program written for an ATtiny85 using
 * Arduino IDE and the 'attiny' board found at: https://github.com/damellis/attiny
 * 
 * For more on the ATtiny85, see: https://www.microchip.com/wwwproducts/en/ATtiny85
 * 
 * The program turns on (in order) the Red LED, waits for 5 seconds, then turns on
 * the Green LED, waits for 5 seconds, then turns on the Yellow LED, waits for 2.5
 * seconds and repeats cycle.
 * 
 * The ATtiny85 was programed with the external programer, and is running is at a
 * clock speed of 1MHz (internal).
 * 
 * The circuit is powered by an external DC buck converter running at 3.3v.
 * 
 * *********************************************************************************
 * 
 * Required Hardware:
 * 
 * - 1x 1330 ATtiny85-20pu
 * - 1x Red LED
 * - 1x Yellow LED
 * - 1x Green LED
 * - 1x 220ohm Resistor
 * - 1x Breadboard
 * - 8x Jumper Wires
 * 
 * Simplified ATtiny85 Pinout:
 * (Note: the dot next to the Reset pin, represents the dot on the chip.)
 *              ______
 *     Reset - |.     | - 5v+
 *    A3 - 3 - |      | - 2 - A1
 *    A2 - 4 - |      | - 1 - PWM
 *       GND - |______| - 0 - PWM
 *
 * 
 * *********************************************************************************
 * 
 * Changelog:
 * 
 * 2020-02-15 - 0.1.2 - Change program to boot with the Red light first.
 *                    - Change Red & Green delay to 5 seconds, and Yellow to 2.5.
 * 2020-02-02 - 0.1.1 - Correct minor spelling and white space cleanup.
 * 2020-01-30 - 0.1.0 - Initial Release.
 * 
 * 
 * *********************************************************************************
 * 
 * MIT License
 * 
 * Copyright (c) 2020 Matt Rude <matt@mattrude.com>
 * 
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 * 
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 * 
 * *********************************************************************************
 */

// Set pin assignments for the ATtiny85 chip.
int redLed = 0;
int yellowLed = 1;
int greenLed = 2;

// The Setup Routine
void setup() {
  // Initialize the digital pins as Outputs.
  pinMode(greenLed, OUTPUT);
  pinMode(yellowLed, OUTPUT);
  pinMode(redLed, OUTPUT);  
}

// The Loop Routine.
void loop() {
  digitalWrite(redLed, HIGH);     // Turn the Red LED on.
  delay(5000);                    // Wait for 5 seconds.
  digitalWrite(redLed, LOW);      // Turn the Red LED off.
  digitalWrite(greenLed, HIGH);   // Turn the Green LED on.
  delay(5000);                    // Wait for 5 seconds.
  digitalWrite(greenLed, LOW);    // Turn the Green LED off.
  digitalWrite(yellowLed, HIGH);  // Turn the Yellow LED on.
  delay(2500);                    // Wait for 2.5 seconds.
  digitalWrite(yellowLed, LOW);   // Turn the Yellow LED off.
}