From 1a515237afb7ad09353a65f5fbc6e98a7c29ce8e Mon Sep 17 00:00:00 2001
From: Kai Stevenson <kai@kaistevenson.com>
Date: Sat, 22 Aug 2026 15:00:35 -0700
Subject: sim manager refactor

---
 src/sim/particle_manager/mod.rs      | 85 ++++++++++++++++++++++++++++++++++++
 src/sim/particle_manager/particle.rs | 21 +++++++++
 2 files changed, 106 insertions(+)
 create mode 100644 src/sim/particle_manager/mod.rs
 create mode 100644 src/sim/particle_manager/particle.rs

(limited to 'src/sim/particle_manager')

diff --git a/src/sim/particle_manager/mod.rs b/src/sim/particle_manager/mod.rs
new file mode 100644
index 0000000..e5e47eb
--- /dev/null
+++ b/src/sim/particle_manager/mod.rs
@@ -0,0 +1,85 @@
+use crate::{
+    config::PIXELS_TO_METRES,
+    sim::{
+        cell::{cell::Cell, materials::MaterialForm},
+        cell_manager::manager::CellManager,
+        lib::ray::AwDda,
+        particle_manager::particle::Particle,
+    },
+};
+
+pub mod particle;
+
+pub struct ParticleManager {
+    pub particles: Vec<Particle>,
+}
+
+const PARTICLE_GRAVITY: f32 = 9.81 * PIXELS_TO_METRES;
+
+impl ParticleManager {
+    pub fn tick(&mut self, world: &mut CellManager, delta_time: f32) {
+        puffin::profile_function!();
+        let mut i = 0;
+        'outer: while i < self.particles.len() {
+            let p = &mut self.particles[i];
+
+            p.life -= delta_time;
+            if p.life <= 0.0 {
+                self.particles.swap_remove(i);
+                continue 'outer;
+            }
+
+            p.velocity.y += PARTICLE_GRAVITY * delta_time;
+            let dt_velocity = p.velocity * delta_time;
+
+            let mut dda = AwDda::new(p.position, p.position + dt_velocity);
+
+            if let Some(mut prev) = dda.next() {
+                if let Some(cell) = world.get_cell_from_game_position(prev.x, prev.y)
+                    && [
+                        MaterialForm::Solid,
+                        MaterialForm::Powder,
+                        MaterialForm::Liquid,
+                    ]
+                    .contains(&cell.material.def().form)
+                {
+                    // the particle is already inside a collider, we should just kill it
+                    self.particles.swap_remove(i);
+                    continue 'outer;
+                }
+
+                for next in dda {
+                    if let Some(cell) = world.get_cell_from_game_position(next.x, next.y)
+                        && [
+                            MaterialForm::Solid,
+                            MaterialForm::Powder,
+                            MaterialForm::Liquid,
+                        ]
+                        .contains(&cell.material.def().form)
+                    {
+                        // write ourselves to the board
+                        world.set_cell_from_game_position(
+                            prev.x,
+                            prev.y,
+                            Cell::from_material(p.material),
+                            false,
+                        );
+                        self.particles.swap_remove(i);
+                        continue 'outer;
+                    }
+                    prev = next;
+                }
+            }
+
+            // no collision, just move
+            p.position += dt_velocity;
+            i += 1;
+        }
+    }
+
+    pub fn new() -> Self {
+        ParticleManager {
+            particles: Vec::new(),
+        }
+    }
+}
diff --git a/src/sim/particle_manager/particle.rs b/src/sim/particle_manager/particle.rs
new file mode 100644
index 0000000..cc7dd28
--- /dev/null
+++ b/src/sim/particle_manager/particle.rs
@@ -0,0 +1,21 @@
+use glam::Vec2;
+
+use crate::sim::cell::materials::MaterialId;
+
+pub struct Particle {
+    pub position: Vec2,
+    pub velocity: Vec2,
+    pub material: MaterialId,
+    pub life: f32,
+}
+
+impl Particle {
+    pub fn new(position: Vec2, velocity: Vec2, material: MaterialId, life: f32) -> Self {
+        Particle {
+            position,
+            velocity,
+            material,
+            life,
+        }
+    }
+}
-- 
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