From this book, http://docs.finance.free.fr/Options/Exotic_Options_Trading.pdf, it states that

The gamma profile of a Max lookback option becomes intuitive when viewing it as a ladder option. Indeed, as long as the stock goes up there will be gamma on the lookback option and the gamma will decrease quickly when the stock goes down, as the options below have already knocked out and therefore have no gamma on them any more.

I just cannot see how this is intuitive nor why there will be gamma on the lookback option as long as the stock goes up. What I am missing here? I cant picture how this gamma would change with spot and time.