Oo-day ou-yay eak-spay ig-pay atin-lay? If that sentence looks like gibberish to you, you’ve got your first taste of how fun a secret code can be. Codes and ciphers look like nonsense to an untrained eye, but they hide a secret message for the receiver. Plus, it’s a great way for kids to play with language and letters!

This round-up of 7 secret writing codes will give you plenty of ideas for your next family night. Choose a code or cipher to write a message in, then send it to a friend or family member to see how quickly they can decode it.

1. Pig Latin

Pig latin is one of the most popular English code languages, in part because it’s so easy to learn. To speak or write it, all you have to do is move the first letter from the beginning of the word to the end and add “-ay.”

If you’re looking for a code you can learn quickly, pig latin might be your best bet. Check out this video from Go Noodle to perfect your pig latin knowledge.

2. Book Cipher

This cipher is simple to use because all you need is a pencil, a piece of paper, and a good book.

Find the first word of your message in the book and write down the page number, line number, and position of the word in the line. Keep doing this until you’ve put together an entire sentence—with notes for how to find each word. Then, give the person a copy of the book and your notes so they can have fun deciphering your code.

Creating your first book cipher can take a little time. But once you get the hang of it, it can be a creative way to exchange codes with your friends or family. The video below provides a great overview of book ciphers and how to get started.

3. Morse Code

This secret code has plenty of history behind it. Originally, it was used to transmit telegraph messages and played a crucial part in World War II.

Although Morse code is traditionally tapped out, its dots and dashes can also be written. Northeastern University has a Morse code chart and online resource for beginners that can help you get started.

4. Decoder Wheel

One of the best-known examples of a secret code is the decoder wheel. This fun tool assigns a number to each letter of the alphabet. Once you’ve written out a message in code, hand it and the decoder wheel over to a friend so they can translate it.

Ready to make your own decoder wheel? Use this print-out from Dabbles and Babbles to try it out.

5. Invisible Ink

Invisible ink can be an exciting way to create a secret message. Your friend or family member will delight as a hidden message suddenly becomes visible before their eyes! Most invisible inks are readable through certain light sources or solutions.

Use the video below to mix up an invisible ink solution made from lime juice that can be read by candlelight.

6. Caesar Cipher

Caesar ciphers are especially popular for children because they’re easy to understand. Plus, they’re a great way to practice the alphabet.

All you have to do is rotate the alphabet by a number of your choice so each letter can be translated to a different one. If your rotation number is “2,” for example, the letter “A” would now correspond to “C.”

This resource from Scholastic is a great way to learn more about and create your own Caesar cipher.

7. Create Your Own Code

If none of the above codes or ciphers are clicking for you, maybe it’s time to make your own. You can choose any symbols, special inks, or decoding tools you want to make a code that only your friends or family can crack. You could, for example, pick a shape to represent each letter of the alphabet.

PBS Utah has an excellent article on creating your own secret code to help you make one that works for you.