Most people associate a charity marathon with months of training ending in a gruelling test of endurance.
But Tommy Refenes has done it from the comfort of his front room in America.
When his sister launched a fundraising page to help their diabetic mum buy an alert dog, Tommy took it upon himself to walk some of the largest maps in gaming to help out.
His efforts ended with a six-hour stint on Grand Theft Auto V (GTA V) as he strolled across Los Santos.
Tommy, who is the co-creator of indy game Super Meat Boy, also spent two hours and nine minutes walking across the map of Red Dead Redemption and took four hours and 19 minutes to complete the length of Grand Theft Auto San Andreas.
Below the live stream of the fundraiser, the gamer wrote that his mum "is having a lot of trouble with her Type 1 Diabetes and an alert dog could help her out and improve her health tremendously".
He added: "The dogs are trained to recognise smells due to high and low blood sugar and alert their owner.
"Mom has lost the ability to do this on her own which could be potentially very dangerous for her.
"After 32 years of having diabetes, it's becoming almost impossible for her to tell when her sugar is going low or high. This is potentially a fatal condition."
Following Tommy's efforts the fundraiser page had broken the $15,000 (£9,307) target by $677 (£420) with 112 days remaining.