examples: add fireworks example (#8358)

examples/fireworks/modules/objects/rocket.v

@@ -0,0 +1,68 @@
+module objects
+
+import gg
+import gx
+import rand
+
+pub struct Rocket {
+pub mut:
+	color     gx.Color
+	pos       Vector
+	vel       Vector
+	accel     Vector
+	exploded  bool
+	particles []Particle
+	dead      bool
+}
+
+pub fn (rocket Rocket) draw(mut ctx gg.Context) {
+	ctx.draw_circle(rocket.pos.x, height - rocket.pos.y, rocket_radius, rocket.color)
+}
+
+pub fn (mut rocket Rocket) explode() {
+	rocket.exploded = true
+
+	for _ in 0 .. offspring_count {
+		rocket.spawn_particle()
+	}
+}
+
+pub fn (mut rocket Rocket) tick(mut ctx gg.Context) {
+	if !rocket.exploded {
+		if rocket.vel.y <= 1 {
+			rocket.explode()
+		}
+
+		rocket.accel += gravity
+		rocket.vel += rocket.accel
+		rocket.pos += rocket.vel
+		rocket.draw(mut ctx)
+
+		rocket.accel = {}
+	}
+
+	for mut particle in rocket.particles {
+		particle.tick(mut rocket, mut ctx)
+	}
+}
+
+pub fn new_rocket() Rocket {
+	return Rocket{
+		color: random_color()
+		pos: {
+			x: rand.f32_in_range(50, width - 50)
+		}
+		vel: {
+			x: rand.f32_in_range(-1.5, 1.5)
+			y: rand.f32_in_range(5, 7)
+		}
+	}
+}
+
+pub fn (mut rocket Rocket) spawn_particle() {
+	rocket.particles << Particle{
+		color: rocket.color
+		pos: rocket.pos
+		accel: random_vector_in_circle().mult(2)
+	}
+}