Content reference: demo v0.5.4
If the game does not start
Launch the game and allow the first download to finish. This is a Unity WebGL build with large data and WebAssembly files, so a blank frame during a slow first download is different from a completed load followed by an error. Check your connection, then retry once. If an extension blocks game requests, test with that extension disabled for this site.
If it loads but will not respond
Click inside the game so it receives input. Close menus with Escape or Tab and test basic movement before testing locked abilities. Rolling requires the Sprinting upgrade, so walking without rolling can be normal. If the canvas remains black, try a current browser with WebGL enabled and hardware acceleration available; do not repeatedly reset your save to diagnose graphics.
If the forest becomes slow
Use the original options menu’s graphics and audio settings, close heavy background tabs and compare a smaller window with fullscreen. The demo has many animated objects; the v0.5.0 notes describe pooling and rendering improvements, not a guarantee of identical performance on every machine. A phone-sized webpage does not prove physical-phone compatibility. Record browser, device, build and the stage of failure if the issue persists.