What Makes Casino Games So Easy to Pick Up and Play?
There’s a light show on at the Landmark until the 27th. Luxmuralis is projecting the history of time across the inside of the old St Alban’s church, and if you go you’ll notice how many people in the nave are looking at their phones as well as the ceiling. The phone is where most of us check things now, and it’s been designed so that checking takes no thought at all.
Teddington has a claim on this subject. The first working caesium atomic clock was built up the road at NPL in 1955 by Louis Essen and Jack Parry; the Science Museum’s record of it gives its accuracy as a second in three hundred years, and every phone clock descends from it. A year earlier an American psychologist called Paul Fitts had worked out that the time it takes to hit a target depends on how far away it is and how big it is, and that the relationship is regular enough to write down as a formula. Essen measured time. Fitts measured the finger. Between them they explain why a game on a phone feels instant.
Signals, not instructions
The games people play on the train from Teddington station don’t come with manuals, and the reason is that the screen is doing the explaining. The design writer Don Norman calls the things that tell you what to do “signifiers”: a button that looks pressable, a tile that looks draggable, a slot shaped like the piece that fits it. Most casual games are built from little else.
Table games had a head start here, because their layouts were built to explain themselves long before anyone had a screen. A roulette cloth is a diagram of every bet on offer: 37 numbers in red, black and a single green, columns and dozens marked along the edges, evens and odds in their own boxes, and on the European table a racetrack for the bets that follow the wheel round. Nothing on it needs a caption. The difficulty is size. The people who build roulette games online have to fit those 37 numbers and the outside bets onto a screen about 390 points wide without any square shrinking below what a fingertip can hit, and that number, it turns out, has been measured.
How big is a number?
Apple’s design guidance says a control should be at least 44 points square so a finger can land on it. Google says 48 density-independent pixels, which comes out at about nine millimetres on any screen. The W3C’s accessibility standard, in a note updated in May, sets a floor of 24 by 24 CSS pixels. Fitts’s formula is why those numbers exist: shrink the target and the time to hit it rises in a curve you can plot, and a game that makes you miss is a game you close.
Feedback is the other half. A tap has to be answered with an animation and, on most phones, a click you can feel, quickly enough that the two feel like one event. The threshold for “instant” was measured too, decades ago, at about a tenth of a second; slower than that and the hand starts to doubt the screen.
Deciding less
What the good casual games share is how little they ask per turn. One word a day. One digit in a sudoku grid. One chip on one square. Monument Valley, the ustwo puzzle game that passed 26 million downloads, took most reviewers under three hours and never asks you to remember the previous screen. The big strategy games on the same phone, with their menus and their wikis, are built for a different evening. One fits a train journey and the other doesn’t.
Any screen, same game
The layout also has to survive a tablet, a laptop and a phone turned sideways, and the browser does more of that work than it used to. Responsive layouts reflow the cloth rather than shrinking it, touch and mouse are handled by the same code, and the animation runs at the screen’s own refresh rate or it gets noticed. NPL’s clock was checked against the turning of the Earth. A game’s timing gets checked against a thumb, which is less forgiving.
What Teddington measured
The games that last are the ones you understood before you knew you were learning them, and Teddington, of all places, has the instruments to prove it. NPL opened Bushy House to a few thousand visitors last September to show off 125 years of measuring things that go unnoticed. The light show at the Landmark runs until the 27th.