platform-jump · diff
git:20260912.a76815a to git:20260913.624182f
21 added, 37 removed. Audit A to A.
---
name: platform-jump
- description: >
- Coyote, jump buffer, variable height, corner slip. Use when a jump feels
- floaty, late, or unfair. Stacks on locomotion and action-feel
- coyote-platformer. Do not copy a franchise stage.
+ description: Use when a platformer's jump arc, rise/fall gravity, takeoff speed, air control, jump cut, or reachable-gap metrics need outcome-based tuning.
---
# Platform jump
- Ask the column.
+ This skill owns the **jump arc and reachability metrics**. `jump-leniency` owns coyote time, input buffering and corner forgiveness; `locomotion` owns movement integration and grounding.
- | Column | Accel | Forgiveness |
- |---|---|---|
- | snap-run | almost instant | coyote + buffer |
- | weight-run | long accel / stop | coyote only |
- | inertia-air | keep air momentum | dash edges extra |
- | gravity-flip | local up vector | same timers |
+ Choose the movement/jump feel:
- Tune by **outcome**: height in body-heights, time-to-apex in seconds. Not by a raw gravity you copied.
+ | Column | Ground feel | Air policy |
+ |---|---|---|
+ | snap-run | fast acceleration | authored air control |
+ | weight-run | longer accel/brake | authored air control |
+ | inertia-air | preserves more horizontal momentum | optional air verbs |
+ | gravity-flip | local up vector | same ownership rules in local frame |
- ## Feel knobs (starting points, not law)
+ Tune by outcomes such as body-height jump, time-to-apex and horizontal reach rather than copying raw constants from another game.
- | Knob | Typical start |
- |---|---|
- | height | 2.5–4 body heights |
- | time to apex | 0.28–0.40 s |
- | fall gravity | 1.5–2.0× rise |
- | coyote | 5–8 frames @ 60 |
- | jump buffer | 6–10 frames |
- | jump cut | release multiplies upward vel by ~0.4–0.5 |
+ For a simple constant-gravity arc using positive magnitudes:
- ```
- gravity_up = 2 * height / apex^2
- v0 = 2 * height / apex
- gravity_down = gravity_up * fall_mul
+ ```text
+ gravity_up = 2 * height / apex_time^2
+ launch_speed = 2 * height / apex_time
```
- Levels must be beatable **without** coyote. Coyote is a late-press save, not a hidden extra tile.
-
- ## Clock
-
- Coyote and buffer live on the same logic tick as action-feel. They are not render-time slop.
- Corner correction is a small horizontal nudge when a jump clips a lip. It is not a magnet through a wall.
+ A separate fall multiplier or curve may be authored. These equations are a starting model, not a requirement for every jump system.
- ## Iron rules
+ ## Rules
- - Variable height is cut-upward-velocity on release, not "release to jump".
- - Buffer consumes on the first grounded frame, then clears.
- - Spikes / pits that require coyote as the only legal jump are a level-design bug.
- - Dash / wall-jump are named extra verbs. They do not silently rewrite jump height.
+ - Variable-height jump cut belongs to the arc policy; its input edge comes through `input-design`/movement state.
+ - Coyote/buffer configuration is referenced from `jump-leniency`, not duplicated here.
+ - Dash, wall-jump and double-jump are separate named verbs/capabilities; they do not silently rewrite the base arc.
+ - Critical level geometry should be validated against the intended no-forgiveness baseline unless the design explicitly requires a forgiveness mechanic as a taught capability.
## Accept
- A player who presses one frame late still jumps. A player who taps gets a short hop. A spectator can tell intended jumps from coyote saves in training-mode.
+ Measure height, apex time, horizontal reach and short-hop outcome from logical state. Verify representative gaps under the intended movement column, with forgiveness disabled and enabled separately. Changing render FPS does not change the arc; changing leniency does not secretly change gravity or takeoff speed.