Tetris

What it is. Seven shapes fall one at a time; rotate and slot them so rows fill and clear. There is no end, no story, no unlock — just a board, a next piece, and a speed that climbs the longer you last.

Player fantasy / why it’s fun. One more line. The pull is flow through mastery of a single verb: the rules fit on a napkin, but the skill ceiling is bottomless, and the game tightens exactly as fast as you improve. It is the cleanest proof that depth doesn’t need breadth.

Design DNA

Take one verb — orient-and-drop — and tune it until it’s perfect, then let difficulty rise with the player’s own success. Every cleared line speeds the fall; skill buys you time that the game immediately taxes back. There’s no meta, no content treadmill: the loop is so tight and so well-tuned that repetition is the reward. The randomiser (a bag of 7) keeps it fair; the failure state (stack to the top) is always your doing.

The discipline here is subtraction. Tetris is the proof that depth doesn’t require breadth — that a single verb, tuned to perfection, out-lasts games with a hundred mechanics. Everything that isn’t the drop was cut: no story to gate the loop, no unlocks to pace it, no second verb to dilute the tuning budget. All of that budget goes into feel — the exact frames of lock delay, the DAS charge, the gravity curve, the rotation kicks — because when there’s one verb, the game is its feel.

This is the ur-example of easy to learn, impossible to master — the entire game is a mastery curve with the fat trimmed off. And the ramp is self-tuning: because speed scales with your clears, the game meets every player at their edge without a difficulty menu. The flow channel holds for a beginner and a world-record holder using the identical rule.

Load-bearing structures

Structure	Why it works
One verb, perfectly tuned	Orient + drop is the whole moveset. All design budget goes into feel — DAS, lock delay, gravity — not breadth. `system-mastery-curve`.
Success raises difficulty	Clearing lines speeds the fall; the game auto-escalates to match you, so flow holds across skill levels. FUN.md law: the ramp is the design. `system-difficulty-and-dda`.
Self-inflicted failure	You lose by stacking to the top — always legibly your mistake. No cheap deaths, so retry is instant appetite.
Bag randomiser	The 7-bag guarantees fairness (no piece drought) while staying unpredictable — controlled randomness. All rng via `world.rng` (FUN.md law). `system-procgen-design`.
The next-piece queue	Showing what’s coming turns reflex into planning — a one-cell telegraph that opens the skill ceiling. `system-telegraphs`.
Lock delay + soft/hard drop as grace	A frame window to slide/rotate before a piece sets — the grace canon that makes fast play fair. FUN.md law 5. `system-grace`.
The score as the whole meta	No progression system; the leaderboard number is the entire long-term goal. `system-collectibles` (score-as-goal).

What to steal

Pick one verb and spend everything on its feel. Lock delay, buffer, gravity curve, rotation system — the tuning is the game. Depth without breadth.
Let difficulty rise with success. Tie the ramp to the player’s own score/clears so flow self-corrects across all skill levels — no difficulty menu needed.
A fair randomiser (bag, not pure-random). Guarantee no droughts so failure is always skill, never luck. Route it through world.rng.
A lookahead queue to convert reflex into planning and lift the ceiling. Showing the next piece (or several) is a one-cell telegraph that lets skilled players pre-solve placements — depth added with zero extra rules. See system-telegraphs.
Make the failure state self-inflicted and instantly re-enterable. Cheap, legible death is the engine of “one more go” — you always know why you lost, and you’re one keypress from trying again.
Cut everything that isn’t the verb. Resist the urge to bolt on story, meta, or a second mechanic; every addition steals tuning budget from the one thing players actually feel. Scope discipline is the design.

What’s just theme (drop it)

The Soviet / cosmonaut branding. Pure decoration.
The specific 7 tetrominoes. A small alphabet of shapes with a fair bag is structural; the exact set is tuning — a hexagonal or pentomino variant obeys the same DNA.
The music (Korobeiniki). Iconic, but the loop is silent-viable — it’s a pattern-juice-choreography layer, not a mechanic.
The board being 10×20. Dimensions are tuning, not law.

Composes into

genre-grid-puzzle — shares the grid-and-piece substrate (though endless, not solved-level).
system-mastery-curve — the purest “easy to learn, hard to master” exemplar.
system-difficulty-and-dda — success-driven auto-escalation.
pattern-mastery-and-flow — the flow channel held by a self-tuning ramp.
system-grace — lock delay / drop buffering.

Twist seams

Tetris but the pieces are your deck (mechanic-swap) — you draft/upgrade which tetrominoes can appear; the bag becomes a build. Pulls in genre-deckbuilder depth over the pure verb.
Tetris but two boards share a rising garbage line (perspective) — clears send junk to a rival; the single-verb duel becomes competitive. Feeds system-coop-and-competition.
Tetris but gravity is a resource you spend (constraint) — you choose when the piece falls, and hesitation costs a meter; converts reflex into economy. Bends the auto-fall that defines the genre.
Tetris but tonal — you’re stacking to build, not to clear (tonal) — filling rows raises a tower/city that persists instead of vanishing; the same orient-and-drop verb, recolored from anxiety-management into gentle construction. Pairs with genre-city-builder.