A game is easier to judge and to play without the editor around it. The Game tab and the game link now both have a button that puts the game view itself into fullscreen, not just the browser window. - The Game tab header has a fullscreen button on the right. It hides toolbar, panels, tab headers and console and keeps the zoom from the picker. A running game keeps running. - A corner button at the top right, or Esc, leaves fullscreen and puts the view back into the tab where it was. - The game link shows the same corner button. Over a running game it hides after 2 s without mouse movement and returns on the next move. - A click on the corner button never reaches the game. - Stop ends fullscreen. Stop switches back to the Scene tab, and any switch away from the Game tab ends fullscreen, so no empty screen is left behind. - src/viewport/fullscreen.ts wraps the Fullscreen API and holds the rule for when the button shows. FullscreenCorner.ts is the button used by both pages. Two SVG icons are new. - Editor.showGameFullscreen moves the GameViewport into the root while fullscreen is on. Tests: - ./check.sh: 195 files, 2815 tests, exit 0 (3 new unit tests). - e2e 60: 2 new checks for the corner button on the game link. - e2e 61 (new): 4 checks for fullscreen in the editor. - Full e2e run (local): ALL PASSED, 1580 checks. - Counter-checks fail as expected: rule without "no game running", no stopPropagation (60h), no end on tab switch (61c), no reparenting of the view (61a). Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>