Hi,

Why are you using strings as output?

• it's not detailed in the description (which makes it wrong, btw)
• it adds an useless extra layer to the task

Other than that:

• The limitation on x and y can be avoided by explaining you're using chars in ASCII order. Tho if you got that way, you should rather use uppercase letters, so taht you actually can have strings with printable chars as output (hence, you'd still need som contraints to keep x+y low enough, like below 60)
• the description is a btit convoluted. Might be better to give the example first, then explain how it's built. At the very least, change the 3 examples column ...: row ... -> because you and them with "and so on" while you're not "moving" in a row or a column with them. That makes the explaination quite confusing.