This game is a homebrew parser game. It seems expansive at first, intimidatingly so, but it soon settles down to a fairly small, nice-sized map.
Unfortunately, the possibility space of commands is fairly high. In most modern parser games, Inform or TADS take care of common synonyms (LOOK AT vs. X vs. EXAMINE, TAKE vs. GET, etc.), and new verbs are generally hinted at in the text or provided by using items where only one word works (a shovel leads to DIG, for instance), and extensive beta-testing finds all synonyms a general player might use. This fails at times, frequently even, but it is a standard that is widespread among Inform/TADS authors.
Games written in other engines tend not to have this flexibility (with Robin Johnson's Versificator parser games being a notable exception). The standard synonyms in Inform and TADS are the results of hundreds of hours of work and playtesting, and even well-established rival engines like Quest and Adrift fail to come close to their standards. And personally written parsers tend to have even more trouble.
This is a long-winded way of saying that there are a lot of commands I wouldn't have guessed on my own without the walkthrough. Besides that, I adored this game. Crossing the chasm reminded me of The Neverending Story for some reason, finding the island reminded me of the first Zelda game. A fun slice of enjoyment.