Installing Escape Velocity Inside a Browser Tab

September 2026 · Andrew Nakas

Most of the Macintosh shareware of the late 1990s cannot be unpacked on a modern computer. Download Escape Velocity from an archive and you get a StuffIt file, and inside that an installer: an application built with Installer VISE, whose data fork begins with the four bytes SVCT. No tool on a modern Mac, Windows or Linux machine reads that format. The only thing that can open it is the thing it was written for: a Macintosh, running the installer.

So that is what this site does. Nine Ambrosia Software games went up this week, Escape Velocity, EV Override, Ares, Mars Rising and more, and every one of them was installed by booting Mac OS 8.6 in a browser tab and running Ambrosia's own installer inside it.

A Mac that a script can drive

The emulator is SheepShaver, compiled to WebAssembly by the Infinite Mac project, the same one that runs the games for visitors. For installing, a page boots a work disk: a copy of Mac OS 8.6 with an extra folder holding the installers. A Playwright script then drives the emulated Mac the way a person would: double-click the disk, double-click the Installers folder, double-click an installer.

The useful discovery was how little the script needs to know. Every Installer VISE screen of that era has a default button: Continue on the splash, Accept on the licence, Install on the options, Quit on "Installation was successful". Pressing Return walks through all of them. One sequence of Returns, repeated for each installer in the folder, installed five games in a single boot. The exception was Ares, whose licence screen has no default button, so Return does nothing and the installer sits there forever. That one needs a click on Accept.

Clicks themselves need care. The emulated Mac polls the mouse rather than receiving events, so a click that goes down and up inside one frame is often never seen. The script moves the pointer, waits, presses, waits a quarter of a second, and releases.

Getting the result back out

The work disk is saved as the emulator runs, into the browser's origin private file system, as two files: the disk's data, and a bitmap recording which 256-kilobyte chunks the Mac has written to. After the installs the script shuts the Mac down properly from the Special menu, because a volume killed mid-write comes back damaged, then reads out only the chunks the bitmap marks as dirty. Installing five games touched about 35 to 50 megabytes of a 700-megabyte disk.

Those chunks are laid over the original image, and the installed folders are copied from the result onto one small disk per game. On that disk the application is renamed "Start App", with an alias called "Start" beside it, so that the shared operating system can launch it at startup. Nothing else is changed: every game is exactly what Ambrosia's installer wrote, shareware notice and all.

One operating system for all of them

Every Mac OS 8 game here mounts the same Mac OS 8.6 disk. Disks are stored as content-addressed chunks, so a visitor downloads the operating system once and every other title reuses it from the browser's cache. That same property made the next fix cheap.

Watching Avara boot frame by frame showed a dialog nobody had reported: "Rebuilding the desktop file…", on the shared system disk, for forty seconds or more, on every start. The disk had been built by a Python library that writes no desktop database, and because the shared disk is never saved, Mac OS rebuilt it again on every visit, for every one of the 32 games that use it. The fix was to boot that disk once, let the Finder finish, shut down cleanly, and keep the result. Only 17 chunks changed, so a returning visitor downloads 4.3 megabytes rather than the whole system again.

What comes next

EV Nova, Deimos Rising and Pillars of Garendall are Carbon applications and need Apple's CarbonLib. The same technique installed it: an authoring page saved the system disk while the CarbonLib installer ran from a second disk, and the result differs from the shared system by 30 chunks. They need more than that, though: newer Game Sprockets for Deimos Rising, QuickTime 4 for Pillars, and something still unidentified for EV Nova. That is the next job.

Until then, the games that are here are complete and free to play, under the licence Ambrosia shipped with each of them: non-profit distribution, unmodified, complete. Click Not Yet on the shareware notice, and you are in.