PLS HELP HUHU

SO THERES A MANHWA I THINK AND ITS ACTION THAT I READ A LONG TIME AGO AND THE PLOT IS THAT THERES THIS GUYS THAT IS TRAPPED IN A CUBE AND LIKE WHEN HE COMPLETED THE TUTORIAL HE STILL CANT GET OUT AND HE STILL CONTINUE THE TUTORIAL UNTIL HE GETS SO STRONG THAT HE BREAK THROUGH THE CUBE AND WHEN HE SEE THE OUTSIDE WORLD ITS VERY DIFFERENT ALSO THE MC HAS WHITE HAIR