1 files changed, 24 insertions, 0 deletions
diff --git a/src/content/materials/gas.rs b/src/content/materials/gas.rs
new file mode 100644
index 0000000..229d0e9
--- /dev/null
+++ b/src/content/materials/gas.rs
@@ -0,0 +1,24 @@
+use rand::RngExt;
+
+use crate::sim::cell_manager::sim::{PostUpdateAction, UpdateCtx};
+
+#[inline]
+pub fn sim_update(ctx: &mut UpdateCtx) -> PostUpdateAction {
+    // only allow upward movement some of the time to limit movement speed
+    if ctx.rng.random_range(0.0..1.0) > 0.8
+        && ctx.swap_or_settle(&[(0, -1)]) == PostUpdateAction::None
+    {
+        return PostUpdateAction::None;
+    }
+    // same for each horizontal direction
+    if ctx.rng.random_range(0.0..1.0) > 0.8
+        && ctx.swap_or_settle(&[(1 - ctx.seqno_parity as i32 * 2, 0)]) == PostUpdateAction::None
+    {
+        return PostUpdateAction::None;
+    }
+    if ctx.rng.random_range(0.0..1.0) > 0.8 {
+        return ctx.swap_or_settle(&[(-1 + ctx.seqno_parity as i32 * 2, 0)]);
+    }
+
+    PostUpdateAction::Apply
+}