CHALLENGE 3: Re-Triggering a One-Shot Particle Burst Twice
====================================================================

TASK
----
Add a one-shot GPUParticles2D to a scene. Write a function that
calls restart() on it, and call that function twice in a row a
second apart (using await and a timer) to confirm a fresh burst
genuinely happens both times, not just the first.

SETUP
-----
1. Add a GPUParticles2D node.
2. In the Inspector, under "Emission Shape" / general particle
   settings, enable "One Shot".
3. Configure a short "Lifetime" (e.g. 0.5s) and a reasonable
   "Amount" (e.g. 20) so the burst is clearly visible.

SOLUTION CODE (attached to the GPUParticles2D)
---------------------------------------------------
extends GPUParticles2D

func _ready() -> void:
    burst()
    await get_tree().create_timer(1.0).timeout
    burst()

func burst() -> void:
    restart()

OBSERVED RESULT
----------------
A visible particle burst plays immediately when the scene starts,
finishes (since one_shot is enabled and Lifetime is short), and then
a second, completely fresh burst plays again exactly 1 second later -
not a silently-ignored no-op.

WHY THIS WORKS AS AN ANSWER
----------------------------
This is a direct demonstration of the chapter's own warning: simply
setting emitting = true a second time would NOT produce a second
burst here, because a one_shot particle system that has already
finished its single emission won't start a new one just because
emitting is set back to true - that only resumes a continuous effect
that had been paused.

restart(), by contrast, genuinely begins a brand-new emission cycle
each time it's called, which is exactly why it's the correct choice
for a repeatable effect like this - an impact spark that should
visibly fire again on every hit, not just the very first one. The
await get_tree().create_timer(1.0).timeout pause (Chapter 7's own
pattern) simply spaces the two calls out so both bursts are clearly
visible as two separate events rather than overlapping into what
would look like one longer burst.