The whole publication

Every piece, in seven sections

Twenty-two pieces. No dropdown, no search box — the full register, reachable from the bar at the bottom of the screen.

The Reachable Arc

What one hand can actually touch.

The reachable arcHeld in one hand, the thumb sweeps an arc pivoting at the bottom corner; everything frequent belongs inside it, and the top far corner is the worst real estate on the device.
Touch targetsApple's 44 points and Google's 48dp exist because a fingertip is about a centimetre across and carries no cursor.
OcclusionThe hand covers what it touches, which is why feedback appears above the finger.
One hand versus twoGrip changes with context, and a design that assumes two hands loses the commute.

A commute is the unit.

Session shapeA queue, a commute, a wait — the unit of play is minutes, and structure follows.
InterruptionThe session can end at any instant without warning, so state has to be safe continuously.
ResumptionComing back has to cost nothing; a re-entry that requires remembering is a lost player.

Time as a mechanic.

FarmVille and the clockZynga's 2009 game made the wait itself the mechanic — crops ripen on a timer and spoil if ignored, so the game schedules the player.
Timers as pacingSupercell's Hay Day and Clash of Clans turned waiting into a pacing system with a price attached to skipping it.
The life meterCandy Crush Saga's regenerating lives end the session for you, which is a design decision about when to stop.

Free-to-play as a structure.

The core loopAct, reward, invest, wait — and the fact that the loop is legible to the player is part of why it works.
Free-to-play as structureRemoving the purchase at the door moves every design decision to retention.
What conversion does to designWhen very few players ever pay, the design optimises for the ones who might.

Tutorials and the first session.

The first sixty secondsMost players who leave, leave immediately, so the opening is the most designed part of the game.
Teaching without textConstrained first levels teach by making the wrong move impossible.
Retention curvesDay one, day seven, day thirty — and what those three numbers hide.

Who formalised it.

ZyngaSocial-network games at scale, and the instrumentation-led design practice that came with them.
SupercellSmall independent teams with authority to cancel their own games, and a very short released list as a result.
KingBrowser puzzle games that moved to the phone and took the level-map structure with them.

The arguments against.

Cow ClickerIan Bogost built it in 2010 as a satire — a cow, a click, a six-hour timer — and watched people play it sincerely, which is the most useful thing written about the form.
A Casual RevolutionJesper Juul's argument that casual players are not a lesser audience but a different one, with different tolerances.
Dark patternsWhere pacing becomes pressure, and the design vocabulary for telling the two apart.