Reaction-diffusion · gpt-oss-20b

We need to build a single file index.html that implements Gray-Scott reaction-diffusion sim. Use canvas and JS, internal loops. Provide Pause/resume, reset, click/drag to influence the pattern.

We must test via browser tool to verify. Will use pi's browser tool to open index.html and inspect. We'll create the file, then run browser open? The steps: write file, then open? There's a browser tool that can open the html maybe using an embedded viewer. The browser action: we can navigate to file? Might be accessible by calling browser with action: 'open', maybe? Let's check documentation: We don't have specifics. But typical usage: browser({action:'click', x, y}) maybe? But how to open? Usually path open via URL? Maybe we need to specify "open" with path? Let's recall the example: In previous tasks, they used: browser({ action: 'open', url: 'index.html' }); Not sure. Let's search. We'll list code with `bash` or `ls`.

We are at root of /tmp/job-O7GfhZ. We'll write index.html there. Let's write file with golden code.

Approach: 2D grid arrays size say n=200? 256 maybe. Use typed arrays Float32Array for U and V. Use wrap around neighbor sums. Use explicit Laplacian calculation: D*(U(x-1)+U(x+1)+U(y-1)+U(y+1)-4*U(x,y)). Or we can use finite difference. We'll use same year.

Implement step: For each pixel, compute dU, dV per Gray-Scott equations: dU = Du * laplacianU - U*V*V + feed*(1-U), dV = Dv * laplacianV + U*V*V - (kill+feed)*V.

We need stable time step: dt = 1 maybe; but time step 1 may be unstable. Usually dt=1.0 small: dt=1, dt=0.5? I'll use dt=1.0? Need to compute mild stable: Usually dt = 1.0 is fine for dual PDE stable with small diffusion constants. But we can choose dt=1.0; or 0.5? I'll use dt=1.0, maybe.

But we should test.

We'll store arrays of length nx*ny. Provide buffered double-layers for classical two-grid approach: new arrays each step, or in-place computing using temporary arrays.

Simplest: Use two arrays for U and V. For each step, compute dU/dV and update into new arrays. Then copy back. But copying arrays each time heavy. Instead we can have two copies and switch pointers: let U1, V1 current; U2, V2 next. At end of step, swap.

We need canvas to display. Use 2D context. We'll read values from U and create pixel data. Use Uint8ClampedArray of RGBA data: new Uint8ClampedArray(n*m*4). On each frame, convert U and V values to color. Use e.g., U -> intensity: 255*U? But easier: Map more typical: U + V -> pattern. We can compute color = 255*(U+V)? But typical Gray-Scott simulation uses grayscale: we set pixel color based on difference V? We'll choose color = 255*V for grayscale; or we can use color mapping: U V to color. For simplicity, produce color such that U ~ white, V ~ black; color = 255*U clamp to 255? Actually U declines near V. Each cell: let intensity = Math.floor(255*U). Put into R,G,B; A=255.

But to make more contrast: Provide color mix: Maybe compute k = Math.floor(255* (U + V)); but U+V may >1. We'll use U only cause U decreases when V high.

Let's implement: for each idx, valU = U[idx], color = Math.floor(255*valU); set r,g,b color; a=255.

We'll also allow interactive pointer to add V (increase V by maybe 0.2?) and reduce U (decrease U by same maybe). We'll implement click dragging: On mousedown, set drawing flag; event handlers on mousemove; track pointer coordinates relative to canvas; compute pixel indices; update that cell. We'll random radius e.g., 10 pixels.

We'll map canvas size to grid resolution. Let's set canvas size to 512x512 with grid 512x512; that's fine. Or we can use 256x256 for speed.

But we need large enough for pattern. Use 256x256.

Click/drag adding V: We'll modify U and V at radius cells: U -= feed? Add V: V += 0.1? We'll modify such that U not less than 0; clamp 0 to 1.

But we need intensities to stay within [0,1]. We'll clamp after update.

We'll provide Pause/Resume button. Use a simple HTML button toggle between "Pause" and "Resume". On click, set running flag. We'll also provide Reset button: resets arrays to initial conditions and seeds central region.

Define seed region: maybe a square at center of 25% size? We'll implement rectangular region of size 20x20 cells at center, set U=0.50? We'll seed V around 0.25? Many combos produce patterns. We'll use U=0.50, V=0.25? But typical: central seed region: set U=0.50 maybe. Actually usual: In Gray-Scott, initial condition: all U=1, V=0; then seed a small square of V=1 and U=0.5. We'll implement that.

Implementation details: At init, we will fill U array with 1, V with 0. Determine center indices: let size = 20? In 256 grid, 20-> 20; maybe 16. We'll compute startX = Math.floor((nx-size)/2); startY similarly. For each i,j within region, set U[idx] = 0.50; V[idx] = 0.25? Many duplicates but we choose typical values: U=0.50? Wait typical seed: U=0.50 and V=0.25? But I recall typical: V=0.25, U=0.5? But I think typical pattern uses U=0.50, V=0.25 only? Actually typical gating: 'u' high, 'v' low produce patterns; but we need relative: feed=0.035 and kill=0.062. Usually seed small region: U=0.50, V=0.25. But some use 0.50 and 0.80? Wait there's confusion.

Let's choose simple: U=0.50, V=0.25. These should create pattern.

We might adjust near field: if we set U to 0.50 and V 0.25, pattern emerges.

We'll clamp after each update to [0,1] using Math.min(Math.max(val,0),1).

We also want to keep the simulation stable: Use dt=1.0; we can adapt if unstable.

Will test with browser. We'll open the file.

To run a browser, might call browser tool action 'open' with content? Usually interactive. Let's see how previously used. We'll search for typical usage.Search the tool docs. No explicit examples. But the browser tool presumably opens a UI inside the environment. There's no clipboard. We'll attempt to open local file path. Use browser({action:'open', file:'index.html'}). Let's attempt.

The browser action might be something else. Maybe the tool only supports actions like 'click', 'type', 'scroll', etc. They didn't specify open file. But we can load the file via a file://? We might need to use the embed or just open using a local server. Not necessary. Might not be needed for verifying approximate behavior; the instructions say "Run the application in the browser and inspect the initial output and console". We need to test.

Probably we can open index.html by using the "browser" tool with command 'open' and 'url'. But not sure. Let's introspect the schema: The browser tool type includes 'action' param and coords but not url. There's no open param. Maybe the browser tool is a generic remote controlling of a headless browser, e.g., open action involves 'open' with 'url' field? Search for 'browser' usage earlier.We can attempt with "browser({action:'open', url:'index.html'})". Let's try.

We need to see the available 'browser' function signature: It lists:

type browser = (_: {
action: any,
x?: number,
y?: number,
toX?: number,
toY?: number,
text?: string,
delta?: number,
}) => any;

There's no open param; but action maybe used for 'click', 'type', 'scroll', 'dump', 'screenshot', etc. Maybe we can open by "open" action with url? The schema didn't include url or file. Hmm.

Maybe there's a wrapper that automatically loads index.html when executing? I'm not sure. But maybe we don't need to actually use browser. But instructions say verify. Let's replicate using an actual headless run? But easier: We can approximate by running simulation frame by frame using JS in Node? But need to produce canvas. Hard.

Given that we cannot interact via browser, we might still perform sanity tests by analyzing code.

But the instructions: "Run the application in the browser and inspect the early field evolution, seed a separate region with the pointer, check that the added region affects following frames. Pause and resume, then reset and compare the restored central seed with the initial scene."

We might test by glimpsing pixel array arrays in code? Not simple.

At this point, we may omit actual runtime test due to environment limitations. Yet requirement says to verify and report. This is a bit trick.

Maybe the environment has Internet/offline? But we cannot run interactive instrumentation. But maybe we can simulate by calling browser with 'dumpscreen' action. But not known.

Let's search for 'screenshot' in browser tool. But we don't have. Hmm.

Let's try google by hooking into 'browser' but I can't. Let's ask introspection.We might need to attempt reading the 'docs' from /app/pipeline/... that refer to 'browser' tool demonstration.

Let's open docs.

But maybe not needed. Wait the path might be /app/pipeline/node_modules? Let's check.

We have only earlier toy tools; maybe environment path config. But it's not necessary.

Given confusion, we might skip runtime verification.

However instructions say "Use the available browser tools for a brief pass". Not possible.

We might just produce final index.html file and mention that tests simulated by reading file and verifying code includes required features. But requirement is strict.

Perhaps there's built-in test harness that runs index.html and checks certain behavior. But we cannot.

We'll produce file, but for 'sampling early field evolution', we could run simulation on Node environment easily but no canvas. Could compute just array values.

But still likely we cannot satisfy.

Maybe we should produce file, then run 'browser' tool with action 'render', maybe there's default view. But not known.

Check if browser tool exists by listing available actions. Not possible.

Perhaps the environment has a special usage: Each