Play first, cold. Load like a first-time visitor. Record: time to first input, time to first win/lose feedback, what you understood without instructions, where you got bored. Play twice — once naive, once trying to break it (spam inputs, resize, lose on purpose, idle).
Write the MDA sentence: "This game wants the player to feel X via dynamic Y produced by mechanics Z." Can't write it? That's finding #1 — no essential experience. Then write the loop contract: "player does [verb] to achieve [objective] while [pressure] creates risk; success → [reward], failure → [cost/retry]". Any bracket you can't fill is a finding too.
Run the rejection gates (below). Each failed gate is an automatic blocker — no lens needed.
Pick 8–12 lenses. Always: Essential Experience, Fun, Feedback, Juiciness, Accessibility. Add by genre (Skill vs Chance for arcade, Curiosity for puzzle, the Toy for sandbox/physics).
Answer with evidence — a timestamp, a code path, a missing sound — never vibes.
Severity: blocker (player quits or never understands), major (understood but flat), minor (polish), idea (opportunity).
Findings as lens → evidence → fix, fixes concrete ("80ms hit-stop + 4px shake on collision", not "juicier"). Order: blockers, then cheapest major wins (audio + shake + score popups = highest fun-per-line).
Re-play after fixes, re-asking only the failed lenses and gates.

Rejection gates

Binary go/no-go tests, self-applied in active play before claiming a game is fun. Any "true" = automatic blocker; fix or iterate before polishing:

The first 30 seconds lack a real decision.
The player can ignore the main mechanic and still progress.
The objective is unclear without reading source code or instructions.
Failure arrives before the player can understand why.
Challenge is only "more things", never better combinations.
Rewards change nothing — not strategy, score, progression, or feel.
The space is decorative and shapes no decisions.
The game is fun only in the designer's explanation, not in active play.

The lens battery

(All lenses Schell unless noted; questions paraphrased. "Smell" = the browser-game failure mode.)

Experience

Essential Experience — what experience should this create; does every system serve it? Smell: a feature list, not a game about something.
Emotion — what should the player feel; what's the arc of a 60s session? Smell: second 10 feels identical to second 100; death has no sting.
Fun — which parts are fun in themselves? Is failure fun? Smell: the core verb is a chore — in a 2-minute game the verb IS the game.
Surprise — what subverts expectation; rare events, escalation beats? Smell: run two has seen 100% of the content.
Curiosity — what questions live in the player's mind ("what's at 100 points?")? Smell: nothing teased, no visible next milestone.
The Toy — strip the goals: is it fun to merely fiddle with? Smell: movement functional but dead; nobody would touch it without a score.
Pleasure (pairs with MDA aesthetics) — which pleasures exist (sensation, anticipation, triumph, destruction); which genre-expected ones are missing? Smell: mono-pleasure; no audio at all is the #1 gap.

Systems & emergence (Wright — SimCity/Sims/Spore school)

Possibility Space — would ten players produce ten different outcomes, or is this a corridor wearing a game's clothes? Smell: every run identical by design, not just by lack of content.
Story Generator — can a player recount a session story the designer never wrote? Systems should manufacture anecdotes. Smell: only authored moments are memorable.
Indirect Control — is the player a gardener (shaping conditions, the system answers back) or a typist (commanding outcomes directly)? Smell: total control, zero surprise — data entry with a skin.
Compression — does every simulated variable change a decision the player actually makes? A sim is a caricature: model what generates choices, fake or cut the rest. Smell: simulation detail nobody's choices touch.
Investment — has the player made/named/shaped something they'd be sad to lose, and is it then put at risk? Creative investment manufactures stakes for free. Smell: nothing on screen is "theirs".

Mechanics & structure

Elemental Tetrad — mechanics, story/theme, aesthetics, tech: each pulling weight, in harmony? Smell: solid mechanics in placeholder art, or gorgeous art over a hollow loop.
Unification — what's the theme; what fights it? Smell: prompt-collage — pirate ship, neon UI, fantasy SFX, sci-fi enemies.
Problem Solving — what problems does play pose; do new ones generate each run? Smell: optimal strategy found in 30s, never changes.
Goals — concrete, achievable, layered (next 5s / session / meta)? Smell: "now what?" at spawn; one flat goal.
Meaningful Choices — do choices matter; any dominant strategy? Smell: three weapons, one strictly best; upgrades the player can't perceive.
Simplicity/Complexity — emergent complexity from simple rules, or rulebook bloat? Smell: six mechanics used once each. One verb deep beats five shallow.

Balance & challenge

Flow (after Csikszentmihalyi) — does challenge track growing skill? Smell: difficulty is a constant, not a function of time/score.
Challenge — right for a first-timer; can experts self-select harder play? Smell: novice and expert get the identical experience.
Skill vs Chance — does randomness create drama or injustice? Smell: off-screen spawn deaths; or zero variance, every run identical.
Reward — varied, well-timed, perceptible the instant earned? Smell: points silently increment in a corner.
Punishment — every failure fair and preventable; retry instant? Smell: death → 3 clicks to retry. Target one keypress, <2s.

Feedback & feel

Feedback — for every action, what does the game say back, how fast (<100ms core verbs)? Status always glanceable? Smell: "did that work?" moments.
Juiciness (popularized by Jonasson/Purho) — cascading feedback from minimal input; does it feel alive? Smell: linear motion, vanishing sprites, silent UI. Hand findings to game-feel.
Visible Progress — advancement visible within a run and across runs? Smell: no localStorage best score, no end-of-run stats, no replay hook.

Accessibility & context

Accessibility — cold player sees how to begin in seconds, no manual? Smell: wall-of-text instructions; first 5 seconds kill you while you hunt for the keys.
The Player — who actually plays this; designed for them or the designer? Smell: twitch platformer aimed at casual link-clickers.
The Venue — a browser tab: interruptible, sound-off default, resize, touch AND keyboard, played at work. Smell: runs while tab is blurred, audio never recovers post-gesture, breaks at non-16:9.
Time — is session length right; natural stop/re-entry points? Smell: runs that mathematically never end, or 8-second runs with no arc.

When a human tester is available

Self-play finds structure problems; only a human finds comprehension ones. Protocol: watch live and silently — face and body language outweigh verbal feedback. Never coach, hint, or rescue: 99% of players play unsupervised, so every stumble is a design fault, not a player fault. ~5 testers per build is enough to surface the pattern; fix, then re-test with fresh eyes. Good signs are behavioral: unprompted "one more run", retelling what happened, asking "wait, what if I…".

MDA quick reference

Mechanics (authored rules) → Dynamics (runtime behavior) → Aesthetics (felt emotion). Designers build M→A; players experience A→M — review from the player's side. Eight aesthetics: Sensation, Fantasy, Narrative, Challenge, Fellowship, Discovery, Expression, Submission. Trace every aesthetic failure back to the mechanic causing it: "no tension (A) because no near-misses (D) because hitboxes too forgiving and speed never ramps (M)" — that lands as an implementable change.

Koster cross-check (A Theory of Fun): fun is pattern-learning; mastered = boring. What is the player still learning at minute 1, 3, 5? "Nothing" by minute 1 = no legs, regardless of polish.

Related skills: game-feel (implements Juiciness/Feedback findings), onboarding (implements Accessibility/Flow findings), game-balance (implements Choices/Reward findings), game-playbook (the build recipe).

design-lenses

Design lens review

Procedure