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+# Playground Redesign — 2026 (Design Intent)
+
+> **Purpose of this doc.** Captures design intent of an unfinished playground UI
+> redesign that lived as uncommitted changes in a `MEMLNaut-NISPS_rewound`
+> working copy. The implementation will not be merged into the current vanilla
+> playground — the playground is being rewritten in SolidJS — but the *design*
+> shouldn't be lost. Read this as a feature spec for the SolidJS rewrite, not as
+> a description of current code.
+>
+> **Source snapshot.** `archive/playground-redesign-2026-snapshot` branch in
+> this repo. Single commit `287e3a1` on top of `ddb6b77`. Three files:
+> `playground/a-immersive.html`, `playground/css/a-immersive.css`,
+> `playground/js/a-app.js`. ~1200 lines net of changes.
+>
+> **Status.** Reference-only. Do not merge into the vanilla playground — those
+> files have moved on independently in `main` and a textual merge would be
+> meaningless.
+
+---
+
+## Context
+
+The pre-redesign playground UI was organised around a collapsible **bottom
+sheet** containing a sticky **floating bar** (mode toggles, train/randomize
+buttons, follow toggle, expand chevron). The sheet would expand upward to show
+synth/visual controls. RL thumbs-up/down floating buttons sat just above the
+collapsed sheet at `bottom: 92px`.
+
+The redesign moves to a **right-side macOS-style dock + drawer system** and
+makes the **top heatmap strip directly interactive**. It also adds **undo** for
+RL actions and a **per-parameter override system** that unifies how visual-mode
+and synth-mode parameters can be constrained.
+
+There are five themes, summarised here in decreasing order of architectural
+weight.
+
+---
+
+## Theme 1 — Right-side dock + drawer system
+
+### What changed
+
+Replaces the bottom-sheet pattern with a vertical dock pinned to the right edge
+of the viewport, plus a stack of named drawers that open to the left of the
+dock when their dock icon is activated.
+
+- **Removed:** `<div class="bottom-sheet collapsed">`, `<div class="floating-bar">`,
+  the sheet expand/collapse chevron, sheet-internal sticky mode bar, sheet
+  status line.
+- **Removed JS:** `wireBottomSheet()`, `$bottomSheet`, `$sheetContent`,
+  `$floatingBar`, `$chevronBtn`, `sheetExpanded` state.
+- **Added:** `<div class="dock" id="dock">` with five icon buttons:
+  - `data-drawer="training"` — Training (Add Example, Train, Clear Ex, Clear
+    All, Randomize, plus preset chips: Calm/Chaos, Rainbow, Vortex, Spiral,
+    Embers; loss-canvas section)
+  - `data-drawer="mode"` — Input/Output mode toggles (was the floating-bar
+    pill toggles: Joystick/Hands and Visual/Synth)
+  - `data-drawer="synth"` — Synth controls
+  - `data-drawer="params"` — Engine parameters (see Theme 4)
+  - `data-drawer="help"` — Help
+- **Added:** `<div class="drawer-stack" id="drawer-stack">` containing one
+  `<div class="drawer hidden" data-drawer="…">` per icon, each with a
+  `drawer-header` (title + close ×) and `drawer-body`.
+- **Added JS:** `wireDock()` to hook up icon clicks and drawer close buttons.
+
+### Inferred intent
+
+- Reclaim canvas real estate. The bottom-sheet ate vertical space whenever
+  expanded; a side dock keeps controls flush to one edge and only one drawer
+  opens at a time.
+- Surface mode controls (Visual/Synth, Joystick/Hands) without forcing the
+  user to expand the sheet. Each function lives behind one click on a labeled
+  icon.
+- macOS-dock visual idiom is a familiar metaphor — users intuit
+  "click icon → panel appears."
+- The action-row inside Training drawer (Add Example / Train / Clear Ex /
+  Clear All / Randomize) is grouped by purpose rather than by toolbar real
+  estate constraints, so destructive/dim variants (`.action-btn.dim`) read
+  as secondary.
+
+### Key UX flow
+
+1. Canvas is fullscreen by default, no chrome over it except top heatmap, RL
+   buttons, joystick, and the right dock.
+2. User clicks dock icon → corresponding drawer slides in from the right
+   (between dock and canvas), other drawers close.
+3. User clicks ✕ on drawer header *or* the same dock icon again → drawer
+   closes, canvas is unobstructed.
+4. Mutually exclusive drawers (only one open at a time) keeps the visual
+   hierarchy simple.
+
+### Implementation notes for SolidJS rewrite
+
+- This is the largest theme and pulls HTML, CSS, and JS together. In SolidJS
+  it should naturally become a `<Dock>` component listing icon → drawer
+  pairs, plus a single `<DrawerStack>` rendering whichever is active from a
+  signal.
+- CSS custom properties `--dock-width: 48px` and `--dock-gap: 8px` are
+  introduced; layout (joystick, hand-pip, dev-panel) is offset by these.
+- Old positioning constants — joystick & hand-pip at `bottom: 136px`, RL
+  buttons at `bottom: 92px` — were tied to the collapsed bottom sheet's
+  88px height. With no sheet, they shift down (joystick/hand-pip to 100px,
+  RL buttons to 36px). The rewrite should drive these from layout, not
+  hardcode.
+- `dev-panel` shifts right edge from `right: 16px` to
+  `right: calc(var(--dock-width) + 24px)` to clear the dock.
+
+---
+
+## Theme 2 — Interactive heatmap strip
+
+### What changed
+
+The top heatmap strip — previously read-only visualization of model outputs —
+becomes the primary parameter input surface.
+
+### Two interactions per cell
+
+1. **Drag** (pointermove with motion threshold > 3px) horizontally across a
+   cell → directly sets that parameter's value to the normalized x-position
+   within the cell.
+2. **Click** (pointerup with no motion) → toggles a per-parameter popup with
+   override controls (min, max, curve, freeze).
+
+### Tooltip
+
+Existing tooltip extended:
+- During hover (no drag): shows `{name}: {value}` with a `▾` indicator hinting
+  the bar is clickable.
+- During drag: stays visible and updates live as user scrubs.
+- New CSS: `.heatmap-cell.dragging` with `cursor: ew-resize`,
+  `.heatmap-cell-bar { pointer-events: none }` so child bar doesn't intercept
+  parent pointer events.
+
+### Popup contents
+
+Per-parameter popup (`#param-popup` or similar) built on demand for the
+clicked param:
+- min slider (range 0–1)
+- max slider (range 0–1)
+- curve slider (range 0–1, see Theme 4)
+- freeze toggle — when frozen, dragging the heatmap bar updates a *fixed
+  value* directly rather than going through the model
+- close button / clicks-outside dismissal
+- show/hide handled with `popupHideTimer` (300ms grace period to let user
+  move pointer from heatmap cell into the popup without dismiss-on-leave)
+
+### New JS
+
+- `setHeatmapValue(paramIndex, e, cell)` — converts pointer x to normalized
+  value, applies override semantics (writes to `ov.fixedValue` if frozen),
+  routes outputs, syncs UI.
+- `showParamPopup(paramIndex, cell)` — positions popup near the cell.
+- `hideParamPopup()` — clears active popup state.
+- `wireParamPopup()` — wires popup controls to update underlying override.
+- Tracking globals: `activePopupParam`, `popupHideTimer`.
+
+### Inferred intent
+
+- Make the heatmap a control surface, not just a readout. Saves a trip to
+  the bottom-sheet/drawer for common adjustments.
+- Per-parameter freeze enables hybrid workflow: freeze a few params at fixed
+  values while letting the model drive the rest.
+- Popup is in-context (anchored to the bar) rather than in a side panel,
+  reducing eye travel.
+
+### Key UX flow
+
+- **Quick adjust:** point at heatmap bar → drag horizontally → value changes
+  live, model output reroutes immediately.
+- **Override setup:** click bar → popup opens → adjust min/max to constrain
+  range, or freeze at fixed value, or shape curve (see Theme 4) → click
+  outside or wait for cell pointer-leave to dismiss.
+
+### Notes
+
+- `.heatmap-cell-frozen` CSS class dims frozen cells visually so user knows
+  what's manually overridden.
+- Drag detection uses 3px motion threshold to disambiguate click-vs-drag.
+- Pointer capture (`setPointerCapture`) ensures drag continues even if
+  pointer leaves the cell.
+
+---
+
+## Theme 3 — Undo
+
+### What changed
+
+Adds an undo button below the RL thumbs-up/down buttons, with a 20-step
+history of weight snapshots taken before each RL action.
+
+### Implementation
+
+- New HTML: `<button class="rl-undo-btn" id="btn-undo">` in the RL buttons
+  cluster, with an SVG curl-arrow icon.
+- New CSS: `.rl-undo-btn` (28px circle, dim-by-default at opacity 0.4,
+  brightens to 0.8 on hover, 0.7 when undo is available),
+  `.rl-undo-btn.has-undo` and `.rl-undo-btn.flash` states. Animation
+  `rl-flash` (0.25s ease-out) for feedback after undo.
+- Layout: `.rl-buttons` becomes `display: grid` with two columns and two
+  rows; the undo button spans both columns in row 2 (`grid-column: 1 / -1`)
+  and is centered.
+- New JS:
+  - `const undoStack = []` and `const MAX_UNDO = 20`
+  - `pushUndoSnapshot()` — called before each RL action; clones current
+    weights into the stack; pops oldest if over MAX_UNDO.
+  - `onUndo()` — pops last snapshot, restores weights, flashes button.
+  - `updateUndoButton()` — toggles `.has-undo` class based on
+    `undoStack.length > 0`.
+
+### Inferred intent
+
+- RL actions in this playground are exploratory and easy to "go too far" —
+  e.g. a thumbs-down sequence that drives the model into uninteresting
+  territory. Without undo, user has to retrain or randomize, losing all
+  history.
+- Visual subtlety (low default opacity, only fully visible when there's
+  something to undo) keeps it out of the way until needed.
+
+### Key UX flow
+
+User clicks 👎 → push snapshot, apply update. Result is bad. User clicks
+↶ → restores previous weights. Button flashes briefly to confirm.
+
+### Notes
+
+- This is the cleanest standalone theme — minimal coupling to the rest of
+  the redesign. Consider implementing first in the SolidJS rewrite to
+  validate the snapshot model.
+
+---
+
+## Theme 4 — Per-parameter override generalization
+
+### What changed
+
+Generalizes the existing `groupOverrides` system (which let synth-mode params
+be constrained per-group) to also work in visual mode, and unifies access
+behind a single `getParamOverride(i)` accessor.
+
+### New shapes
+
+- `const visualOverrides = VISUAL_PARAM_NAMES.map(() => ({ min: 0, max: 1, curve: 0.5, frozen: false, fixedValue: 0.5 }))`
+  — one override entry per visual parameter, parallel to the existing
+  per-section/per-param structure on the synth side.
+- `getParamOverride(paramIndex)` — given a heatmap index, returns an object
+  with the same shape regardless of mode:
+  - In `visual` mode: returns the corresponding `visualOverrides[i]` entry
+    directly.
+  - In `synth` mode: looks up `paramToSection[paramIndex]` and returns a
+    proxy onto `groupOverrides[si].params[li]`, with `muted` mapped to
+    `frozen` so the popup UI can be mode-agnostic.
+
+### Renames (cosmetic but indicative)
+
+- `buildRawParams()` → `buildEngineParams()`
+- `$rawParams` → `$engineParams`
+- HTML id `raw-params` → `engine-params`
+
+### New JS helpers
+
+- `syncEngineParams()` — pull current values into the drawer-rendered slider
+  list.
+- `formatEngineVal(v, step)` — display formatting for slider readouts.
+
+### Other change
+
+- `let rlExplorationDecay = 0.97` (was `const`) — runtime-tunable, presumably
+  exposed via an Engine drawer slider.
+
+### Inferred intent
+
+- Visual mode previously had no way to clamp/freeze individual parameters.
+  Synth mode did. The asymmetry forced the heatmap popup to behave
+  differently per mode, which is poor UX.
+- Unifying behind one accessor lets Theme 2's popup code be mode-agnostic.
+- "Engine" terminology generalizes "raw params" to whichever output system
+  is active.
+
+### Notes
+
+- This theme is **coupled to Theme 2** — the popup is what consumes the
+  override accessor. They should ship together (or, in the SolidJS rewrite,
+  be designed together as one feature: "per-parameter constraints + the UI
+  to set them").
+
+---
+
+## Theme 5 — Polish (positioning, status line)
+
+Small adjustments forced by the larger redesign or independent quality-of-life
+fixes:
+
+- **Status line** moves from inside the sheet (`<div class="sheet-status">`)
+  to a free-floating pill anchored at `bottom: 8px`, centered, low-opacity
+  (`#status-line`). Lives outside any drawer; visible always.
+- **Joystick & hand-pip** move from `bottom: 136px` to `bottom: 100px`
+  (sheet no longer takes up vertical space).
+- **RL buttons** move from `bottom: 92px` to `bottom: 36px`, gap from 32px
+  to 12px, layout from flex to 2-col grid (to accommodate the spanning undo
+  button below).
+- **`rlExplorationDecay`** changes from `const` to `let` (see Theme 4).
+- **Heatmap tooltip** gets `▾` suffix to hint clickability and stays visible
+  during drag.
+- **Hand-pip video** loses `/* Hidden — only used as MediaPipe source */`
+  comment on the position-absolute hidden video element. Behavior unchanged.
+
+### Notes
+
+- These are positioning constants tied to the shape of the surrounding
+  layout. The SolidJS rewrite shouldn't carry them forward as literals —
+  derive from layout / CSS variables.
+
+---
+
+## What this redesign does NOT change
+
+For completeness — these survived the redesign untouched:
+
+- Joystick container and joystick interaction logic (`wireJoystick`).
+- Hand tracker / MediaPipe pipeline (`createDevPanel(() => handTracker)`).
+- Synth visualizer canvas (`#synth-vis-canvas`, `SYNTH_SECTIONS`).
+- Loss canvas drawing.
+- Help overlay (`wireHelp`).
+- Group overrides for synth mode (extended in Theme 4, but base mechanism
+  unchanged).
+- Gamepad input.
+- Output mode routing logic (`routeOutputs`, `rawParamValues`).
+
+---
+
+## Summary table for the SolidJS rewrite
+
+| Theme | Carry forward? | How it should land in SolidJS |
+|---|---|---|
+| 1. Dock + drawers | Yes | `<Dock>` + `<DrawerStack>` driven by signal for active drawer |
+| 2. Interactive heatmap | Yes | Heatmap cells as components with pointer-event handlers; popup as a portal anchored to clicked cell |
+| 3. Undo | Yes | Single store with `undo()` action + size cap; trivially reactive |
+| 4. Param override generalization | Yes | One unified store keyed by param index; mode is just a derived accessor |
+| 5. Polish | Re-derive | Don't carry positioning literals; recompute from layout |