The eye is a wonderful thing, refracting and focusing so that we can get an accurate, three-dimensional impression of our surroundings.
Of course, the moment this sophisticated system slips the slightest bit out of alignment, we need constant corrective care. Which, I can tell you, is a bloomin' pain in the backside.
It's an apt thing to talk about in relation to Bulkypix's new puzzler, Optika.
Narrow focusOptika is all about bouncing and refracting light; about redirecting, splitting, bending, and combining it so that the right quantity of the right colour ends up in the right place.
So it's very much like a number of other iOS physics puzzlers you'll have played before. There are too many to name, but the first one that came into my head was golden oldie Enigmo.
There have been more since that have played more explicitly with the light theme, but hopefully you get the idea.
Feature lightThe tutorial does a good job of introducing you to each of the game's many tools. There are simple mirrors, lenses that intensify or even accelerate a light beam, and ones that change its colour.
There's an undeniable joy to bouncing beautifully rendered light beams around here, as well as in watching how each gizmo has an effect on them.
Once you're into the levels proper the game's issues quickly manifest themselves. One is the somewhat mean initial offering - just 20 levels once you've cleared the tutorial phase. You then have to pay for additional level packs.
If this were a freemium game, that would be fine, but with a £1.49 / $1.99 initial price, it feels a little stingy.
Far more of a concern is how fiddly things can get. It can be tough work accessing the right lens when the interface toggles overlap one another - particularly when playing on an iPhone.
Holding a lens upBut the biggest issue is one that often affects physics games.
The ultimate aim here is to have all of the light beams shining on the correct target points for a sustained period, at which point a little timer icon becomes a 'proceed' icon, and you can move on.
The trouble is a level-winning situation can often be a case of making tiny, almost imperceptible shifts in a lens. And when you make a tiny shift one way, it can disrupt the path of the other beams you've successfully rerouted.
Soon you're sat nudging the lens one way and then the other, trying to get it just right. Eventually you wonder if you even have the right solution at all, or whether it just requires a little more nudging.
On one level I played, the 'proceed' icon was flipping into view at random, leaving me in the ridiculous situation of hovering over the button, waiting for my moment to escape the level.
It's perhaps the unfortunate result of creating an extremely precise, exacting game for a decidedly imprecise touchscreen input.
Optika is a solid enough game, but its familiar premise, lack of generosity, and inability to overcome some predictable control and interface issues mean that it doesn't manage to shine.