09 Particle Effect

In this chapter, we will spawn a hit particle when a note reaches the judgment line.

Shared Particle

The play section already declared Particles.note. Watch mode reuses that particle effect.

Playing

In play mode, a tap triggers the particle effect. During normal watch playback, a note leaves its active range when it reaches the judgment line. Sonolus then calls terminate, so watch mode can spawn the particle from that callback.

Edit guide/watch/note.py. Add is_skip to the existing runtime import and add the shared particle import:

from sonolus.script.runtime import is_skip, scaled_time

from guide.lib.particle import Particles

Then add terminate after update_parallel:

class WatchNote(WatchArchetype):
    # ...

    def terminate(self):
        if is_skip():
            return

        particle_layout = Rect.from_center(
            Vec2(0, 1),
            Vec2(4 * Config.note_radius, -4 * Config.note_radius),
        )

        Particles.note.spawn(particle_layout, duration=0.3)

Seeking can also make a note leave its active range. is_skip() returns True while Sonolus processes that transition, so the guard prevents a spurious hit effect. At this checkpoint, replay misses still produce particles. Chapter 10 will suppress them after the recorded judgment is available.

Let a note reach the line without seeking: it should produce a particle. Then seek across a note in either direction: the skipped note should not produce a particle.