Mission 18 · Stage 2

Simon Says

sequence compare with input

Watch a growing LED sequence, then repeat it with matching buttons.

Pin connections

Part 1		Part 2
Arduino pin 2	→	Red button pin 1
Red button pin 2	→	Arduino GND
Arduino pin 3	→	Green button pin 1
Green button pin 2	→	Arduino GND
Arduino pin 4	→	Yellow button pin 1
Yellow button pin 2	→	Arduino GND
Arduino pin 5	→	Blue button pin 1
Blue button pin 2	→	Arduino GND
Arduino pin 8	→	Red resistor pin 2
Red resistor pin 1	→	Red LED anode (+)
Red LED cathode (-)	→	Arduino GND
Arduino pin 9	→	Green resistor pin 2
Green resistor pin 1	→	Green LED anode (+)
Green LED cathode (-)	→	Arduino GND
Arduino pin 10	→	Yellow resistor pin 2
Yellow resistor pin 1	→	Yellow LED anode (+)
Yellow LED cathode (-)	→	Arduino GND
Arduino pin 11	→	Blue resistor pin 2
Blue resistor pin 1	→	Blue LED anode (+)
Blue LED cathode (-)	→	Arduino GND

See it

Repeat the growing pattern!

Watch the LED sequence, then press matching buttons — one step longer each round.

Memory games train pattern matching — same idea as Simon toys.

The story

The problem

You must compare each input to a stored sequence step by step.

Think of it like

Like “Simon says” — copy the pattern or you are out.

Meet the parts

Runs your sketch

Arduino

Brain

Loading part…

Matches red in the sequence

Red button

Input

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Matches green in the sequence

Green button

Input

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Matches yellow in the sequence

Yellow button

Input

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Matches blue in the sequence

Blue button

Input

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Shows red in the pattern

Red LED

Output

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Shows green in the pattern

Green LED

Output

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Shows yellow in the pattern

Yellow LED

Output

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Shows blue in the pattern

Blue LED

Output

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Protects red LED

Red resistor

Safety

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Protects green LED

Green resistor

Safety

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Protects yellow LED

Yellow resistor

Safety

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Protects blue LED

Blue resistor

Safety

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How it works

Play sequence

Flashes LEDs in order from the sequence[] array.

showSequence();

Read your button

Each press maps to an index 0–3 matching an LED color.

digitalRead(BTN_PINS[i]) == LOW

Compare step

Wrong button triggers fail; correct adds another random step.

if (i != sequence[step]) failPattern();

Then loop back to step 1

Build the circuit

Follow these steps in order. Match the wires to the colors shown.

1
Place Arduino
Place the Arduino (uno) on the breadboard.
Arduino placed!
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2
Place Red button
Place the Red button (btn0) on the breadboard.
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3
Place Green button
Place the Green button (btn1) on the breadboard.
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4
Place Yellow button
Place the Yellow button (btn2) on the breadboard.
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5
Place Blue button
Place the Blue button (btn3) on the breadboard.
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6
Place Red LED
Place the Red LED (led0) on the breadboard.
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7
Place Green LED
Place the Green LED (led1) on the breadboard.
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8
Place Yellow LED
Place the Yellow LED (led2) on the breadboard.
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9
Place Blue LED
Place the Blue LED (led3) on the breadboard.
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10
Place Red resistor
Place the Red resistor (r0) on the breadboard.
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11
Place Green resistor
Place the Green resistor (r1) on the breadboard.
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12
Place Yellow resistor
Place the Yellow resistor (r2) on the breadboard.
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13
Place Blue resistor
Place the Blue resistor (r3) on the breadboard.
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14
Connect Arduino pin 2 to Red button (btn0) 1.l
Connect Arduino pin 2 to Red button (btn0) 1.l.
15
Connect Red button (btn0) 2.l to Arduino GND
Connect Red button (btn0) 2.l to Arduino GND.
16
Connect Arduino pin 3 to Green button (btn1) 1.l
Connect Arduino pin 3 to Green button (btn1) 1.l.
17
Connect Green button (btn1) 2.l to Arduino GND
Connect Green button (btn1) 2.l to Arduino GND.
18
Connect Arduino pin 4 to Yellow button (btn2) 1.l
Connect Arduino pin 4 to Yellow button (btn2) 1.l.
19
Connect Yellow button (btn2) 2.l to Arduino GND
Connect Yellow button (btn2) 2.l to Arduino GND.
20
Connect Arduino pin 5 to Blue button (btn3) 1.l
Connect Arduino pin 5 to Blue button (btn3) 1.l.
21
Connect Blue button (btn3) 2.l to Arduino GND
Connect Blue button (btn3) 2.l to Arduino GND.
22
Connect Arduino pin 8 to Red resistor (r0) 2
Connect Arduino pin 8 to Red resistor (r0) 2.
23
Connect Red resistor (r0) 1 to Red LED (led0) anode (+)
Connect Red resistor (r0) 1 to Red LED (led0) anode (+).
24
Connect Red LED (led0) cathode (-) to Arduino GND
Connect Red LED (led0) cathode (-) to Arduino GND.
25
Connect Arduino pin 9 to Green resistor (r1) 2
Connect Arduino pin 9 to Green resistor (r1) 2.
26
Connect Green resistor (r1) 1 to Green LED (led1) anode (+)
Connect Green resistor (r1) 1 to Green LED (led1) anode (+).
27
Connect Green LED (led1) cathode (-) to Arduino GND
Connect Green LED (led1) cathode (-) to Arduino GND.
28
Connect Arduino pin 10 to Yellow resistor (r2) 2
Connect Arduino pin 10 to Yellow resistor (r2) 2.
29
Connect Yellow resistor (r2) 1 to Yellow LED (led2) anode (+)
Connect Yellow resistor (r2) 1 to Yellow LED (led2) anode (+).
30
Connect Yellow LED (led2) cathode (-) to Arduino GND
Connect Yellow LED (led2) cathode (-) to Arduino GND.
31
Connect Arduino pin 11 to Blue resistor (r3) 2
Connect Arduino pin 11 to Blue resistor (r3) 2.
32
Connect Blue resistor (r3) 1 to Blue LED (led3) anode (+)
Connect Blue resistor (r3) 1 to Blue LED (led3) anode (+).
33
Connect Blue LED (led3) cathode (-) to Arduino GND
Connect Blue LED (led3) cathode (-) to Arduino GND.

Try it

Watch the color order first — then press matching buttons.
Wrong press blinks all LEDs — sequence resets.

Peek at code

Sequence storage

const int BTN_PINS[] = {2, 3, 4, 5};
const int LED_PINS[] = {8, 9, 10, 11};
const int NUM = 4;
const int MAX_LEN = 6;
int sequence[MAX_LEN];
int seqLen = 1;
int step = 0;
enum Phase { SHOW, INPUT };
Phase phase = SHOW;

sequence[] holds the pattern; seqLen grows as you succeed.

showSequence()

void showSequence() {
  for (int i = 0; i < seqLen; i++) {
    flash(sequence[i], 350);
    delay(180);
  }
}

Plays each stored index by flashing the matching LED.

Input compare

void loop() {
  if (phase == SHOW) {
    showSequence();
    step = 0;
    phase = INPUT;
    return;
  }
  for (int i = 0; i < NUM; i++) {
    if (digitalRead(BTN_PINS[i]) == LOW) {
      delay(180);
      flash(i, 250);
      if (i != sequence[step]) {
        failPattern();
        return;
      }
      step++;
      if (step >= seqLen) {
        seqLen++;
        if (seqLen > MAX_LEN) {
          seqLen = MAX_LEN;
        }
        sequence[seqLen - 1] = random(0, NUM);
        phase = SHOW;
      }
      while (digitalRead(BTN_PINS[i]) == LOW) {
        delay(10);
      }
    }
  }
  delay(20);
}

INPUT phase checks each press against sequence[step] — core Simon logic.

Show full sketch (simon-says.ino)

const int BTN_PINS[] = {2, 3, 4, 5};
const int LED_PINS[] = {8, 9, 10, 11};
const int NUM = 4;
const int MAX_LEN = 6;
int sequence[MAX_LEN];
int seqLen = 1;
int step = 0;
enum Phase { SHOW, INPUT };
Phase phase = SHOW;
void flash(int idx, int ms) {
  digitalWrite(LED_PINS[idx], HIGH);
  delay(ms);
  digitalWrite(LED_PINS[idx], LOW);
  delay(120);
}
void showSequence() {
  for (int i = 0; i < seqLen; i++) {
    flash(sequence[i], 350);
    delay(180);
  }
}
void failPattern() {
  for (int blink = 0; blink < 3; blink++) {
    for (int i = 0; i < NUM; i++) {
      digitalWrite(LED_PINS[i], HIGH);
    }
    delay(200);
    for (int i = 0; i < NUM; i++) {
      digitalWrite(LED_PINS[i], LOW);
    }
    delay(200);
  }
  seqLen = 1;
  sequence[0] = random(0, NUM);
  phase = SHOW;
}
void setup() {
  for (int i = 0; i < NUM; i++) {
    pinMode(BTN_PINS[i], INPUT_PULLUP);
    pinMode(LED_PINS[i], OUTPUT);
  }
  randomSeed(analogRead(0));
  sequence[0] = random(0, NUM);
}
void loop() {
  if (phase == SHOW) {
    showSequence();
    step = 0;
    phase = INPUT;
    return;
  }
  for (int i = 0; i < NUM; i++) {
    if (digitalRead(BTN_PINS[i]) == LOW) {
      delay(180);
      flash(i, 250);
      if (i != sequence[step]) {
        failPattern();
        return;
      }
      step++;
      if (step >= seqLen) {
        seqLen++;
        if (seqLen > MAX_LEN) {
          seqLen = MAX_LEN;
        }
        sequence[seqLen - 1] = random(0, NUM);
        phase = SHOW;
      }
      while (digitalRead(BTN_PINS[i]) == LOW) {
        delay(10);
      }
    }
  }
  delay(20);
}

Quick quiz

Q1. Where does repeating work belong?

A. loop() ✓
B. setup()
C. pinMode only

Why: Correct—loop() runs again and again.

Q2. What happens when you press the wrong button?

A. failPattern() resets the game ✓
B. The sequence gets longer
C. Nothing — it ignores wrong presses

Why: Correct — wrong input fails and sequence length goes back to 1.

Code lab — try on your own

Slow the show — change flash delay 350 to 500 in showSequence (inside flash call line 18).
Hint: Line 18.
Comment line 56 explaining wrong button check.
Hint: if (i != sequence[step])

Code walkthrough

A line-by-line tour of the sketch — the same steps as in Robo Gurukul Studio.

Program overview

Technical

Sketches have globals, then setup() once, then loop() forever.

In this project

Watch a growing LED sequence, then repeat it with matching buttons.

Why here

Read from top to bottom. Hover words or lines for help!

const int BTN_PINS[] = {2, 3, 4, 5};
const int LED_PINS[] = {8, 9, 10, 11};
const int NUM = 4;
const int MAX_LEN = 6;
int sequence[MAX_LEN];
int seqLen = 1;
int step = 0;
enum Phase { SHOW, INPUT };
Phase phase = SHOW;
void flash(int idx, int ms) {
  digitalWrite(LED_PINS[idx], HIGH);
  delay(ms);
  digitalWrite(LED_PINS[idx], LOW);
  delay(120);
}
void showSequence() {
  for (int i = 0; i < seqLen; i++) {
    flash(sequence[i], 350);
    delay(180);
  }
}
void failPattern() {
  for (int blink = 0; blink < 3; blink++) {
    for (int i = 0; i < NUM; i++) {
      digitalWrite(LED_PINS[i], HIGH);
    }
    delay(200);
    for (int i = 0; i < NUM; i++) {
      digitalWrite(LED_PINS[i], LOW);
    }
    delay(200);
  }
  seqLen = 1;
  sequence[0] = random(0, NUM);
  phase = SHOW;
}

setup()

Technical

Runs one time when the board turns on.

In this project

Sets up pins and libraries for Simon Says.

Why here

One-time setup belongs here—not in loop().

void setup() {
  for (int i = 0; i < NUM; i++) {
    pinMode(BTN_PINS[i], INPUT_PULLUP);
    pinMode(LED_PINS[i], OUTPUT);
  }
  randomSeed(analogRead(0));
  sequence[0] = random(0, NUM);
}

loop()

Technical

Runs again and again after setup() is done.

In this project

This is the main action you see in Simon Says.

Why here

Repeating work (blink, read sensors) goes here.

void loop() {
  if (phase == SHOW) {
    showSequence();
    step = 0;
    phase = INPUT;
    return;
  }
  for (int i = 0; i < NUM; i++) {
    if (digitalRead(BTN_PINS[i]) == LOW) {
      delay(180);
      flash(i, 250);
      if (i != sequence[step]) {
        failPattern();
        return;
      }
      step++;
      if (step >= seqLen) {
        seqLen++;
        if (seqLen > MAX_LEN) {
          seqLen = MAX_LEN;
        }
        sequence[seqLen - 1] = random(0, NUM);
        phase = SHOW;
      }
      while (digitalRead(BTN_PINS[i]) == LOW) {
        delay(10);
      }
    }
  }
  delay(20);
}

Try this: Change numbers in loop(), then compile and run the simulator.

pinMode

Technical

Tells a pin if it listens or drives something.

In this project

Gets the Simon Says circuit ready in the simulator.

Why here

Goes in setup() because we only set pins once at the start.

    pinMode(BTN_PINS[i], INPUT_PULLUP);

digitalWrite

Technical

Turns a pin ON or OFF.

In this project

Controls lights, motors, or buzzers in Simon Says.

Why here

Goes in loop() so it can keep changing while the program runs.

  digitalWrite(LED_PINS[idx], HIGH);

digitalRead

Technical

Checks if a pin is ON or OFF.

In this project

Reads buttons or sensors in Simon Says.

Why here

Goes in loop() so we can react when something changes.

    if (digitalRead(BTN_PINS[i]) == LOW) {

analogRead

Technical

Reads a sensor number from 0 to 1023.

In this project

Turns a sensor signal into a number for Simon Says.

Why here

Goes in loop() to keep checking the sensor.

  randomSeed(analogRead(0));

delay

Technical

Waits for some time. Nothing else runs during the wait.

In this project

Controls speed so you can see Simon Says in the simulator.

Why here

Right after an action that should stay the same for a moment.

  delay(ms);

random

Technical

Picks a random number in a range.

In this project

Adds randomness in Simon Says.

Why here

In loop() when you want different values each time.

  sequence[0] = random(0, NUM);

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