Skip to main content
Create a retro-style LED clock that displays the current time using ASCII art and animates in real-time.

​
What You’ll Build

An animated terminal clock that:
  • Displays the current time using LED-style ASCII art
  • Updates every second
  • Shows hours, minutes, and seconds
  • Includes blinking separators (bonus feature)
  • Clears and redraws smoothly

​
What You’ll Learn

  • Working with arrays and multi-dimensional data structures
  • Using the time package to get and format time
  • Creating animations in the terminal
  • Screen clearing and cursor control
  • Type definitions for code organization
  • Infinite loops with for

​
Step-by-Step Approach

1

Print the Digits

Create ASCII art representations of digits 0-9 and print them side-by-side.
// Define a placeholder type for LED digits
type placeholder [5]string

// Create digit 0
zero := placeholder{
    "███",
    "█ █",
    "█ █",
    "█ █",
    "███",
}

// Create digits 1-9...
// Put them all in a digits array
digits := [10]placeholder{
    zero, one, two, three, four,
    five, six, seven, eight, nine,
}
Tasks:
  • Define a new placeholder type
  • Create digit arrays from 0 to 9
  • Store them in a “digits” array
  • Print them side-by-side
2

Print the Clock

Get the current time and display it using your LED digits.
// Get the current time
now := time.Now()
hour, min, sec := now.Hour(), now.Minute(), now.Second()

// Create the clock array with separators
clock := [8]placeholder{
    digits[hour/10], digits[hour%10],
    separator,
    digits[min/10], digits[min%10],
    separator,
    digits[sec/10], digits[sec%10],
}

// Print the clock
for line := 0; line < 5; line++ {
    for _, digit := range clock {
        fmt.Print(digit[line], "  ")
    }
    fmt.Println()
}
Tasks:
  • Get the current time using time.Now()
  • Extract hours, minutes, and seconds
  • Create the clock array
  • Add separator characters (like ”:”)
3

Animate the Clock

Make the clock update every second.
import "github.com/inancgumus/screen"

// Clear the screen once
screen.Clear()

// Infinite loop to update the clock
for {
    // Move cursor to top-left
    screen.MoveTopLeft()
    
    // Get current time and display
    // ... (clock drawing code)
    
    // Wait one second
    time.Sleep(time.Second)
}
Tasks:
  • Create an infinite loop
  • Update the clock every second
  • Clear the screen before starting
  • Move cursor to top-left before each update
4

Blink the Separators (Bonus)

Make the ”:” separators blink on and off.
// Toggle separator visibility
sep := separator
if time.Now().Second()%2 == 0 {
    sep = placeholder{" ", " ", " ", " ", " "}
}
Tasks:
  • Toggle separators based on odd/even seconds
  • Create an empty placeholder for “off” state

​
Complete Example

Here’s a simplified version showing the key concepts: 
package main

import (
	"fmt"
	"time"
	"github.com/inancgumus/screen"
)

func main() {
	type placeholder [5]string

	// Define digits 0-9 (abbreviated here)
	zero := placeholder{"███", "█ █", "█ █", "█ █", "███"}
	one := placeholder{"██ ", " █ ", " █ ", " █ ", "███"}
	// ... define two through nine
	
	separator := placeholder{" ", "█", " ", "█", " "}
	
	digits := [10]placeholder{
		zero, one, /* two through nine */
	}

	screen.Clear()

	for {
		screen.MoveTopLeft()
		
		now := time.Now()
		hour, min, sec := now.Hour(), now.Minute(), now.Second()

		clock := [8]placeholder{
			digits[hour/10], digits[hour%10],
			separator,
			digits[min/10], digits[min%10],
			separator,
			digits[sec/10], digits[sec%10],
		}

		for line := range clock[0] {
			for index, digit := range clock {
				fmt.Print(digit[line])
				
				if index != len(clock)-1 {
					fmt.Print("  ")
				}
			}
			fmt.Println()
		}

		time.Sleep(time.Second)
	}
}

​
Key Concepts

// Define a custom type for cleaner code
type placeholder [5]string

// Now you can use it like any other type
var digit placeholder
digit = placeholder{"a", "b", "c", "d", "e"}
This makes the code more readable and type-safe.
num := 42

tens := num / 10  // 4 (integer division)
ones := num % 10  // 2 (modulo/remainder)

// Works for any two-digit number
// 59 -> 5 and 9
// 07 -> 0 and 7
The github.com/inancgumus/screen package provides:
  • screen.Clear() - Clear the entire screen
  • screen.MoveTopLeft() - Move cursor to (0,0)
Install it with:
go get github.com/inancgumus/screen

import "time"

// Get current time
now := time.Now()

// Extract components
hour := now.Hour()     // 0-23
min := now.Minute()    // 0-59
sec := now.Second()    // 0-59

// Sleep/pause execution
time.Sleep(time.Second)        // 1 second
time.Sleep(time.Millisecond)   // 1 millisecond

​
Output Example

███  ███     ███  ███     ███  ███
█ █    █  █  █      █  █  █ █  █  
█ █    █     ███    █     ███  ███
█ █    █  █    █    █  █    █    █
███  ███     ███  ███     ███  ███
This displays 01:15:08 in LED style!

​
Challenges & Tips

Common Issues:
  • Screen flickering: Make sure to use screen.MoveTopLeft() instead of screen.Clear() in the loop
  • Import errors: Install the screen package with go get
  • Time format: Remember that hours are 0-23 (24-hour format)
Enhancements to Try:
  • Add 12-hour format with AM/PM
  • Show the date below the time
  • Use different colors (with ANSI codes)
  • Add a digital clock alongside the LED version
  • Make the blink rate configurable

​
Practice Exercises

After completing the project, try these exercises:
  1. Refactor - Split the code into functions
  2. Alarm - Add an alarm feature that beeps at a specific time
  3. Split Second - Show milliseconds
  4. Ticker - Use time.Ticker instead of time.Sleep

​
Resources

​
Next Steps

Bouncing Ball

Create another animation project

Arrays Guide

Learn more about arrays

Build docs developers (and LLMs) love

Get started for freeTalk to us