The mother of a student kicked to death for being a Goth has launched an animated film which re-enacts the brutal attack.

Twenty-three black balloons were released into the sky in the city centre on Thursday evening to mark what would have been Sophie Lancaster's 23rd birthday before onlookers watched Sophie: A Dark Angel.

Miss Lancaster, 20, was repeatedly stamped on and kicked in the head by two youths as she cradled her boyfriend, fellow Goth Robert Maltby, who was also assaulted in the incident in a park in Bacup, in August 2007.

She never regained consciousness as she slipped into a coma and died later in hospital. Mr Maltby has made a partial recovery.

More than 100 people gathered in Manchester's Cathedral Gardens and applauded after watching the two-minute movie projected on a big screen.

The film was commissioned by make-up brand Ilamasqua which has supported the Sophie Lancaster Foundation through the sales of Sophie (Stamp Out Prejudice, Hatred and Intolerance Everywhere) black eye pencils and the charity's wristbands. It will also be shown internationally on music channels MTV1 and MTV2.

Miss Lancaster's mother, Sylvia, told the crowd: "This film is to mark Sophie's birthday. This film is not pulling any punches.

"The message is too important, it has to go out there."

She is hoping to raise £500,000 to help educate young people about tolerance through interactive workshops in schools.

The foundation is working with behavioural experts Huthwaite International to devise the programme which will initially be aimed at the 14 to 16-year-old age group, before it is mapped out to primary schools.

A Sophie game has already been developed by the company for use in classrooms as part of the Social and Emotional Aspects of Learning curriculum.

Two youths, aged 15 and 16, were sentenced to life imprisonment in April 2008 for Miss Lancaster's murder.

Three other teenage boys were also jailed for the assault on Mr Maltby.

:: Anyone wishing to make a donation to the charity can visit www.sophielancasterfoundation.com.