Add the Scratch for Java cat as built-in sprites. Its animations - idle, walk, crouch, jump, fall, land, punch, hurt, ko, cheer and climb - load by name, for example addAnimation("walk", "cat_walk_%d", 6). Coffee beans, a bug, a goal mug and hearts for a platformer come with it. The new Cat Platformer example shows them all in a game.

Distribute versioned API, asset and example catalogs, with stable documentation
identifiers, translation overrides and offline example artifacts.

Treat non-finite game speeds as zero and ignore negative elapsed frame time, keeping timers usable after invalid speed input.

Fix windows on Windows with display scaling: Window.useFullScreen() now fills the whole screen instead of a borderless part of it, and windows are centred on the screen instead of partly off it.

Sprites load their costumes without a window, so sizes, costume switching,
hitboxes and clones can be checked in plain unit tests. Without a window,
timers stand at 0.

Variable monitors, like Scratch's "show variable": showVariable("score", () -> score) on a stage or a sprite shows the name and the current value in the top
left corner of the stage, updated every frame, and hideVariable("score")
takes it away. A sprite's monitor says whose variable it is, for example "Cat:
lives".

The game can be paused, stepped and slowed down: Window.getInstance().pause(),
resume(), isPaused(), step() (one frame while paused) and
setGameSpeed(0.5) for half speed. run(), timers, gliding, animations and
timed speech bubbles all follow, so the whole game stands still or runs in slow
motion while the window keeps drawing; keys and clicks still arrive, so a key
can resume the game. Timer.millis() and getDeltaTime() count game time,
which is the real time as long as the game is neither paused nor sped up.

Clones work like Scratch's. clone() makes a clone of the same class (a clone
of a Cat is a Cat, with a copy of its variables), puts it on the stage right
behind the original and runs its new whenStartsAsClone(), "when I start as a
clone". deleteThisClone() removes a clone and leaves the original alone, and
isClone() tells them apart.

public void whenStartsAsClone() {
  this.goToRandomPosition();
}

Before, clone() returned a plain Sprite that was not on the stage, so it
neither showed up nor ran the class's run(). A copy made with new Sprite(other) also drew with the other sprite's pen; it has its own now.

Tiled maps now load CSV and Base64 tile layers, including zlib and gzip compression, tile flips, external tilesets, grouped layers, and class properties. Unsupported map formats now give clearer errors.

A speech or thought bubble now hangs off the top right corner of what is
painted on the sprite's costume, not off its hitbox. A sprite whose hitbox was
set to just its feet - so that it can stand in front of a tree without getting
stuck on it - got its bubble at its feet instead of above its head. The Online
IDE already placed the bubble this way. Collisions still use the hitbox.

A sprite's size now also applies to costumes added after setSize(...).
setSize only resized the costumes the sprite already had, so a sprite that
set its size in the constructor and got its costume later, for example from a
subclass, was drawn at 100 %. addCostume(...) and addCostumes(...) now give
a new costume the sprite's current size, as the Online IDE already did.

Add an NRW version of the library, scratch-<version>-nrw-all.jar, for courses that use the classes of the NRW Zentralabitur. In it, Stage.find, Stage.getAll and Sprite.getTouchingSprites return the Abitur's List instead of java.util.List, so students can write List<Gegner> gegner = find(Gegner.class);. List.java from the Abitur classes has to be in the project's default package. The normal JAR is unchanged.

Stamps are visible again. Everything drawn with a stamp — the layers of a
TiledMap, and Sprite.stamp(...) — passed the ghost effect straight to
Processing as an alpha value, where 0 means "draw nothing" instead of "no ghost
effect". A fully opaque image was therefore stamped fully transparent, which is
why a tile map rendered as an empty stage.

Plain text now sits on the position it was given. It used to be drawn eight
pixels down and to the right of it - the padding a framed style needs between
its border and its words, which plain words have no use for - so a centred label
never landed on the thing it labelled: a number put at the middle of a line came
out beside it. The words are now centred on their position, the way a sprite put
there is.

A width too narrow to hold a single letter no longer wraps the words at all. It
used to turn them into a column of one letter per line: new Text("42", x, y, 1)
drew a 4 above a 2. Line breaks written into the text are still kept.

Text can also be layered like a sprite: goToFrontLayer(), goToBackLayer(),
goLayersForwards(int) and goLayersBackwards(int) decide which of several
overlapping texts is on top. Texts are drawn above the sprites, so this orders a
text against the other texts.

A class that extends Window and has a main method which is not static no
longer fails with "Cannot create multiple Windows!". Since Java 21 the JVM
builds an instance of such a class before it calls main, so the
new MyWindow() inside main was the second window and the project stopped
before it started. That window is now reused, and a note explains how to be rid
of the extra one by making main static. Two windows asked for by the project
itself are still an error.