A man left a baby girl brain damaged after getting "stressed" playing his Xbox, the High Court in Glasgow heard.
Dale Thomson, 27, violently shook the nine-month old child at a flat in Dundee while he was supposed to be looking after her.
A judge heard how the tiny victim will suffer "lifelong implications" as a result of the attack in April.
Thomson pled guilty to attacking the girl to her severe injury, permanent impairment and danger of her life.
The storeman also admitted assaulting a baby boy at another house in the city in October 2010.
He was remanded in custody pending sentencing next month.
The court heard how Thomson had been looking after the girl on 1 April after her mother went to work.
He spent time that day playing an Xbox game online with a teenage boy while the child was asleep.
Prosecutor Paul Kearney said Thomson and the girl's mother went on to exchange text messages.
Mr Kearney said: "He mentioned that the game - which involved trying to complete certain 'missions' - was stressful."
The woman went on to state he looked "raging" after he sent her a photo of him playing the console.
She urged him not to play the game and asked him "not to take his feelings out on others" or she would switch it off on returning home.
Mr Kearney said the exact time of the assault was not known.
At about 14:55 texts suggested "everything appeared well" with Thomson and the child.
But by 15:42 Thomson was making a 999 call insisting the girl's eyes were "rolling" and that she was not breathing.
The baby was rushed to hospital as her relatives were alerted.
Thomson went to claim he had found the girl "floppy" in her cot.
The court heard the child suffered seizures in hospital.
She was transferred to Edinburgh's Sick Children's Hospital where it was discovered she had bleeding on the brain.
Thomson was later quizzed by police and was described as "angry and very agitated".
He "strongly denied" hurting the girl and complained that he was being "unfairly treated".
Thomson was eventually arrested - but insisted police were "corrupt".
Prosecutor Mr Kearney said it was agreed that Thomson "violently shook" the girl causing her head to "rapidly" go back and forwards.
The advocate depute added: "The injury...was severe. It will have lifelong implications impacting on her movement, learning, speech and vision."
The court heard Thomson had already been violent towards another young child.
In October 2010, he had been staying at a flat in Dundee with a baby boy and his mum.
The child woke up crying early one morning before a raging Thomson grabbed him from the seat he was in.
He yelled and swore at the child, questioning why he would not go to sleep.
The baby's mother saw what happened.
Mr Kearney said: "She described it as being done 'with some force - almost in kind of dropping motion. It had been done without supporting the (child's) head."
The boy's mother called police as Thomson claimed he was sorry and that it was "just frustration".
Lord Burns deferred sentencing for reports.