How did they do special effects ion Paranormal Activity movie?

* Practical effects: Many of the effects in Paranormal Activity were created using practical effects, such as the use of props and sets to create a realistic environment. For example, the film's iconic "ghost sheets" were made from ordinary bed sheets that were hung from the ceiling.

* Optical effects: Optical effects, such as camera tricks and editing techniques, were used to create the illusion of supernatural events. For instance, the film's famous "floating chair" scene was created by placing the chair on a hidden platform and then using a camera trick to make it appear as though it was floating in mid-air.

* Sound effects: Sound effects were also used to create a sense of atmosphere and suspense. For example, the film's eerie creaking sounds were created using a variety of techniques, such as recording the sound of old furniture creaking and using computer-generated sound effects.

* CGI: Computer-generated imagery (CGI) was also used to create some of the film's more complex visual effects. For instance, the film's climactic scene, which features a ghostly figure chasing the main character, was created using a combination of CGI and practical effects.