The idea was to create a canvas for people to express themselves with retro pixel art on a grand scale.

But pranksters used a Brighton Digital Festival exhibition to flash insulting messages on a large city centre office building to rail passengers and taxi drivers.

The For The Window project was the brainchild of leading digital firm Brandwatch, who encouraged technophiles to draw designs that would be projected along an 11 metre long LED display board at their offices in Queen’s Road, Brighton.

On Friday night, the LED board was used to insult people heading to catch trains and taxi drivers waiting to pick up customers with four-word expletives.

And other passers-by reported that the sign had been used to draw a giant illuminated rude picture.

Organisers said while there were a few “contentious and predictable” misuses of the tool, the majority of participants were using it in the spirit it was created.

The project has a specially designed website allowing people to draw an image which is then displayed for 15 minutes on the giant screen.

The display was created over three months by Brandwatch staff who wired up and soldered by hand a net curtain of 1,792 led lights and 30m of wire onto 14 wooden frames.

Organisers described the event as a “digital canvas for the community” and are encouraging people to draw art throughout the month of September.

Katja Garrood, creative director of Brandwatch, said: “There were a couple of contentious and predictable pixel pics but luckily they accounted for only a tiny slice of silliness, compared to all the fabulous walking dogs, robots, smiley faces and romantic gestures which entertained and delighted.

“To publish their pixel art, users have to tweet it, so it’s not anonymous and we log all input so we can, if necessary, override what is displayed and block Twitter handles should people choose to abuse it.“