fxgl-shmup

name	fxgl-shmup
description	Build a shoot 'em up (shmup) in FXGL — implement auto-scrolling background for vertical or horizontal scrollers, spawn enemy formations with timer-based waves, fire player bullets toward the scroll direction, script enemy bullet fan/ring/aimed patterns with ProjectileComponent, add power-up collectibles that upgrade weapons (spread shot, laser, shield), implement a lives-and-respawn system, build multi-phase boss fights, track score with chain multipliers, and despawn off-screen entities efficiently. Use this skill when building a space shooter, bullet shooter, vertical shmup, horizontal shmup, forced-scroll shooter, or any game in the shoot 'em up genre.
triggers	["shmup","shoot em up","space shooter","vertical shooter","horizontal shooter","scrolling shooter","formation","wave spawner","bullet pattern","power-up weapon","lives system","boss fight phases","score multiplier"]
compatibility	Java 17+, FXGL 21.x
category	fxgl/game-types
tags	["fxgl","java","javafx","game-types","shmup"]
metadata	{"author":"fxgl-skills","version":"1.0","fxgl-version":"21.1"}
allowed-tools	["Read","Write","Edit","Bash"]

FXGL Shoot 'em Up (Shmup)

Scrolling Background (Vertical Shmup)

// Two background images stacked — when first reaches bottom, second takes over seamlessly
private Entity bg1, bg2;
private static final double SCROLL_SPEED = 120; // pixels per second

@Override
protected void initGame() {
    Image bgImage = getAssetLoader().loadImage("bg_space.png");
    double bgH = bgImage.getHeight();

    bg1 = entityBuilder().at(0, 0)
            .view(new ImageView(bgImage)).zIndex(-1).buildAndAttach();
    bg2 = entityBuilder().at(0, -bgH)
            .view(new ImageView(bgImage)).zIndex(-1).buildAndAttach();
}

@Override
protected void onUpdate(double tpf) {
    bg1.translateY(SCROLL_SPEED * tpf);
    bg2.translateY(SCROLL_SPEED * tpf);

    double bgH = bg1.getHeight();
    if (bg1.getY() >= getAppHeight()) bg1.setY(bg2.getY() - bgH);
    if (bg2.getY() >= getAppHeight()) bg2.setY(bg1.getY() - bgH);
}

Player Ship

@Spawns("player")
public Entity  {
     entityBuilder(data)
            .type(EntityType.PLAYER)
            .view()
            .bbox(BoundingShape.box(, ))
            .with( ())
            .with( ())
            .build();
}

     {
        ;
        ;
          ;  

    
       {
        
        entity.setX(Math.max(, Math.min(getAppWidth() - , entity.getX())));
        entity.setY(Math.max(, Math.min(getAppHeight() - , entity.getY())));

        
        fireTimer += tpf;
         (fireTimer >= FIRE_RATE) {
            fireTimer = ;
            fire();
        }
    }

       {
         (weaponLevel) {
              -> spawnBullet(entity.getCenter(),  (, -));
              -> {
                spawnBullet(entity.getCenter().add(-, ),  (-, -).normalize());
                spawnBullet(entity.getCenter().add(, ),   (, -).normalize());
            }
              -> {
                spawnBullet(entity.getCenter(),  (, -));
                spawnBullet(entity.getCenter().add(-, ),  (-, -).normalize());
                spawnBullet(entity.getCenter().add(, ),   (, -).normalize());
            }
        }
        play();
    }

       {
        spawn(,  (pos.getX(), pos.getY()).put(, dir));
    }
}