1 files changed, 24 insertions, 0 deletions
diff --git a/src/sim/materials/smoke.rs b/src/sim/materials/smoke.rs
new file mode 100644
index 0000000..68f77ca
--- /dev/null
+++ b/src/sim/materials/smoke.rs
@@ -0,0 +1,24 @@
+use rand::RngExt;
+
+use crate::sim::{cell::Cell, materials::MaterialId, sim::UpdateCtx};
+
+#[inline]
+pub fn sim_update(ctx: &mut UpdateCtx) {
+    // only allow upward movement some of the time to limit movement speed
+    if ctx.rng.random_range(0.0..1.0) > 0.8 {
+        if ctx.candidates_swap(&[(0, -1)]) {
+            return;
+        }
+    }
+    // same for each horizontal direction
+    if ctx.rng.random_range(0.0..1.0) > 0.8 {
+        if ctx.candidates_swap(&[(1 - ctx.seqno_parity as i32 * 2, 0)]) {
+            return;
+        }
+    }
+    if ctx.rng.random_range(0.0..1.0) > 0.8 {
+        if ctx.candidates_swap(&[(-1 + ctx.seqno_parity as i32 * 2, 0)]) {
+            return;
+        }
+    }
+}