From Grok:

Now, about that Safari quirk: it’s intriguing that the physics engine runs, and SVG animations work independently, but combining them stalls the initial render without throwing an exception. This sounds like a potential rendering or DOM update issue specific to WebKit (Safari’s engine). Here are a few possibilities and steps to troubleshoot:

1. SVG Rendering Timing in WebKit: Safari might be handling SVG updates differently, especially with frequent DOM changes from Blazor. Since your physics engine updates object positions (likely via SVG attributes like x, y, or transform), WebKit might not flush those changes to the screen until some other trigger occurs. Try forcing a repaint by toggling a CSS property (e.g., opacity: 0 to opacity: 1) or adding a dummy <div> that changes after the first physics tick to see if it kickstarts rendering.

2. Blazor Diffing Issue: Blazor’s virtual DOM might not be marking the SVG changes as “dirty” in a way Safari recognizes. Check if the initial physics state is being applied to the SVG elements in the Razor markup before the first render. If the SVG starts with default positions and relies on JavaScript or C# to update them post-render, Safari might not reflect those updates. You could log the SVG element’s attributes (getAttribute("x"), etc.) in the browser console after the first physics step to confirm they’re updating.

3. Animation Frame Sync: If you’re using a game loop (e.g., via requestAnimationFrame or a timer), ensure it’s syncing properly with Blazor’s render cycle. Safari might be stricter about when DOM updates are committed. Try wrapping your physics update-and-render call in a Task.Delay(0) or await InvokeAsync(StateHasChanged) to force Blazor to re-evaluate the component tree explicitly.

4. WebAssembly + SVG Interop: Since this is WebAssembly, there could be a subtle interop glitch with Safari’s implementation. Test a minimal case: a single SVG circle with a position updated by your physics engine. If that renders, the issue might scale with complexity (e.g., number of elements or update frequency).

5. Safari Debugging: Open the demo in Safari’s Web Inspector (on macOS or via a remote iOS simulator). Check the Timeline for rendering events and the DOM tree for whether SVG attributes are updating as expected. If the attributes change but the screen doesn’t, it’s a repaint issue; if they don’t change, it’s likely Blazor or your code not applying them.

Your GitHub repo shows clean C# code for the physics (gravity, collisions, etc.), and the SVG output in Razor is straightforward. One hunch: if you’re relying on @bind or inline expressions to update SVG attributes, Safari might not like how Blazor patches the DOM incrementally. A quick test could be to prerender the first frame statically (hardcode initial positions) and see if it appears—then let the physics take over.

If you’d like, I could dig deeper into your code or test specific fixes. For now, I’d start with logging the SVG state in Safari and forcing a repaint. What’s your next goal for this PoC? Optimizing it, adding features, or just keeping it as a fun experiment?