In the first season of Stranger Things, a character uses a string of Christmas lights to communicate with a missing loved one. The missing person in question can flash particular lights next to letters painted on a bedsheet to spell out messages. The Christmas lights and bedsheets have become a part of pop culture and because the show is creepy, Redditor BishSaidWut’s recreation is the perfect Halloween decoration.

Unlike most of the similar decorations that you can buy online that either blink randomly or spell out pre-programmed messages, BishSaidWut’s Christmas lights can spell out any message that they text to a specific phone number. That phone number connects to the Twilio service, which parses SMS messages and makes the text available through an API. An ESP8266 board connects to that API and processes incoming messages. If the message is within an acceptable length and doesn’t contain profanity, the ESP8266 passes on the text to an Arduino Uno board. 

The Arduino controls the actual Christmas lights. It buffers text strings that it receives from the ESP8266 and begins animating a new message as soon as the last one finishes. The Christmas lights are all individually addressable RGB LEDs, so the Arduino simply illuminates the LED next to each letter in the proper sequence. BishSaidWut set this up for SMS control so that they could display new messages whenever they like and they’re even considering posting the phone number so others can send their own messages while BishSaidWut streams the results.