Wall Run

What it is. Press into a wall while moving fast and the player runs along it — horizontal or diagonal — instead of falling. It lasts a beat, not forever: gravity claws back, and you exit into a jump or drop off.

Player fantasy. “I don’t stop for terrain.” The wall isn’t an obstacle, it’s a surface you use. Speed becomes a resource that buys you a second path — the room’s architecture turns into a line you get to draw at a run.

The verb

Hold toward the surface while carrying horizontal speed → the run engages, gravity suspends or slows, and you travel until the duration budget drains or you launch. The verb is not “stick to wall”; it’s “spend momentum to defer the fall.”

How it feels

• Borrowed time, not free flight. The pleasure is the countdown — you feel the wall running out and thread the exit before it does. A wall run that never ends is just a floor turned sideways; the fun is the budget.
• Speed in, speed out. Enter slow and it fizzles; enter fast and you rocket. The mechanic rewards the approach, so the level teaches you to set up before you commit.
• Reads as flow, punishes hesitation. Stall on the wall and gravity wins. This is the “keep moving” contract — the mechanic that most makes a room feel like a sentence you speak in one breath. See pattern-mastery-and-flow.

Tuning levers

The two most load-bearing levers are the duration budget (how long the promise lasts) and the gravity ramp (how the promise decays). Get those two shaped right and the rest is polish.

The chaining contract

Wall run only sings when it’s a segment, not a destination. The exit is the point:

• Wall run → jump. The detach launches you outward — often onto the next wall, which starts a fresh budget. Chained walls become a ladder of momentum. This is the seam with mechanic-wall-jump: the run carries you, the jump redirects you.
• Dash → wall run. A mechanic-dash tops up entry speed so a marginal wall engages — the dash pays the entry-speed gate.
• Wall run → dash / air move. Detach with momentum banked so an air option (mechanic-double-jump, mechanic-glide) extends the line past the wall.
• Same-wall lock is what forces the chain: you can’t farm one wall forever, so the level’s walls become a route, not a resting spot. Without the lock, the mechanic collapses into hovering.

Slots into

Pairs naturally with the parkour anchors (mechanic-ledge-grab, mechanic-climb, mechanic-swing) — a traversal kit, not a lone verb. See system-mastery-curve for how a movement toolset builds a ceiling.

Twist seams

• Wall run but only while a note holds on the soundtrack (mechanic-swap) — the duration budget isn’t a timer, it’s the sustained note. Release the wall when the note ends or you drop; the level’s walls are placed to the chart. Fuses traversal with genre-rhythm — the budget becomes music. (See recipe-rhythm-platformer.)
• Wall run but the wall is another player (perspective) — in genre-coop-chaos (anchor-it-takes-two) one player braces and becomes the runnable surface; the runner spends their partner’s stability as budget. The “keep moving” contract becomes a trust contract. See system-coop-and-competition.
• Wall run but the wall runs out from under you (escalation) — surfaces crumble a beat after you touch them (system-hazards-and-environment), so the run creates the pressure it relieves; hesitation isn’t just slow, it’s fatal. See pattern-escalation-and-payoff.

How it wires to Hayao

• Deterministic movement + collision — the run is a state on the mover: detect a wall contact with lateral speed, suspend/ramp gravity, drain a frame budget, resolve the detach impulse. Read sandboxes/physics-lab for the collision + integrator seam; keep all of it deterministic (no wall-clock, no Math.random) so the run replays frame-identical.
• Grace + feel live as framed windows (entry coyote, exit buffer) — spec them in frames and gate them; the recipe is in design/JUICE.md, not here.
• The look — dust off the shoe, a lean into the wall, a speed-scaled trail — is cosmetic. Study sandboxes/juice-lab for the trail / squash vocabulary and sandboxes/camera-lab for the slight lead the camera should give a fast mover. None of it touches world.hash().
• examples/small-flame is the precision-platformer reference for how a momentum verb + grace windows are wired and feel-gated end to end.

Fails when…

• The budget never ends. No drain, no drift, no lock → the wall is a hover pad and the flow evaporates. The countdown is the mechanic.
• The entry is a coin flip. Vague contact/speed detection means the run engages when you didn’t ask and refuses when you did — an antipattern-input-lie. The player must feel that they triggered it.
• It’s mandatory but ungraced. A required wall run with a one-frame window and no coyote/buffer is a antipattern-difficulty-cliff, not a skill test. Grace the entry and the exit (pattern-fairness-and-trust).
• It trivialises the room. If the run skips the whole challenge with no cost, the level stops being a level. Gate it, cost it, or design the room for it.
• It’s decoration. A wall run that leads nowhere — no chain, no shortcut, no time saved — is antipattern-false-depth. If the exit doesn’t open a line, cut the verb.

See also

• mechanic-wall-jump — the redirect that turns a single run into a chain of them; read the two together, they’re one traversal loop.
• mechanic-dash — the momentum injector that pays the entry-speed gate.
• pattern-mastery-and-flow — why “keep moving” reads as flow, and how the budget keeps challenge riding the skill line.
• system-mastery-curve — a movement kit as a skill ceiling; the run is one rung.
• design/JUICE.md — grace windows, trail/camera feel, and the feel-gates that prove the run feels right, not just runs right.