The title of this review sums up roughly 90% of what I have to say about Open Up!; it's a particularly cute and satisfying coda to Birdland. Of course, I could say something about how the characters in Birdland are sufficiently well-executed that it would make me happy that they are happy; but that would really be the domain of a review of Birdland. Play this after playing that one, of course.
In sum: Cute!
...I mean that kindly! Most parser comp entries these days are notably "new school" or newer, but How to Win at Rock Paper Scissors is of some other, earlier school which I will not pretend to taxonomize, since our periodizations seem to change constantly.
What I'm trying to say is. How to Win at Rock Paper Scissors is a fun and funny chilled-out get-X-use-X jaunt, with various lock-and-key puzzles that involve some clever lateral thinking and some notably uninteractive NPCs. It's a relaxing style of game, good for a lunch break, rarely seen in the wild these days. Like its 2007 counterparts, HTWARPS is a little unpolished, but it doesn't much affect one's enjoyment, and the clever error messages are of the more amusing kind.
So, nothing hugely substantial, but good fun. I'm glad that such things are still being made.