String handler comprising: - a random character generator for generating a random character randomly selected from a set of characters; - a memory arranged for storing a string of characters selected from the set of characters, wherein the string has a minimum length of three characters, and marks associated with each character of the string; - an input device for inputting at least one activation tag associated with at least one character of the string; - an output device for conveying an indication to the user; - a controller configured for: - retrieving from the memory the string and when present the marks; - receiving from the input device at least one activation tag; - after receiving the at least one activation tag, receiving from the random character generator the random character; - after receiving the random character, associating a mark with each character in the string if the character equals the random character, and if an activation tag was associated with the character in the string; - after associating and if all characters in the string are associated with a mark, providing an indication to the output device and resetting the string; and - after the preceding step, storing in memory the string and when present one or more marks. - a random character generator for generating a random character randomly selected from a set of characters; - a memory arranged for storing a string of characters selected from the set of characters, wherein the string has a minimum length of three characters, and marks associated with each character of the string; - an input device for inputting at least one activation tag associated with at least one character of the string; - an output device for conveying an indication to the user; - a controller configured for: - retrieving from the memory the string and when present the marks; - receiving from the input device at least one activation tag; - after receiving the at least one activation tag, receiving from the random character generator the random character; - after receiving the random character, associating a mark with each character in the string if the character equals the random character, and if an activation tag was associated with the character in the string; - after associating and if all characters in the string are associated with a mark, providing an indication to the output device and resetting the string; and - after the preceding step, storing in memory the string and when present one or more marks. - retrieving from the memory the string and when present the marks; - receiving from the input device at least one activation tag; - after receiving the at least one activation tag, receiving from the random character generator the random character; - after receiving the random character, associating a mark with each character in the string if the character equals the random character, and if an activation tag was associated with the character in the string; - after associating and if all characters in the string are associated with a mark, providing an indication to the output device and resetting the string; and - after the preceding step, storing in memory the string and when present one or more marks. <EOS>