1 files changed, 11 insertions, 67 deletions
diff --git a/src/sim/cell/materials/gas.rs b/src/sim/cell/materials/gas.rs
index c0cd9f9..2ee7c00 100644
--- a/src/sim/cell/materials/gas.rs
+++ b/src/sim/cell/materials/gas.rs
@@ -1,76 +1,20 @@
+use rand::RngExt;
+
 use crate::sim::cell_sim::sim::UpdateCtx;
 
 #[inline]
 pub fn sim_update(ctx: &mut UpdateCtx) {
-    // if the water can fall, do so
-    if ctx.candidates_swap(&[
-        (0, -1),
-        (-1 + 2 * ctx.seqno_parity as i32, -1),
-        (1 - 2 * ctx.seqno_parity as i32, -1),
-    ]) {
+    // only allow upward movement some of the time to limit movement speed
+    if ctx.rng.random_range(0.0..1.0) > 0.8 && ctx.candidates_swap(&[(0, -1)]) {
         return;
     }
-
-    // if the water can't fall, check if we can move left or right
-    // these are inverted on parity so that we don't preference a direction
-    let left_target = ctx.get_cell(-1, 0);
-    let can_move_left =
-        left_target.is_some_and(|c| c.material.def().density < ctx.material.density);
-    let right_target = ctx.get_cell(1, 0);
-    let can_move_right =
-        right_target.is_some_and(|c| c.material.def().density < ctx.material.density);
-
-    // we can't move down or to other side, so we're stuck
-    if !can_move_left && !can_move_right {
+    // same for each horizontal direction
+    if ctx.rng.random_range(0.0..1.0) > 0.8
+        && ctx.candidates_swap(&[(1 - ctx.seqno_parity as i32 * 2, 0)])
+    {
         return;
     }
-
-    // if we can't move left, just move right
-    if !can_move_left {
-        ctx.candidates_swap(&[(1, 0)]);
-        return;
-    }
-    // and vice versa
-    if !can_move_right {
-        ctx.candidates_swap(&[(-1, 0)]);
-        return;
-    }
-
-    // find the closest hole within 20 pixels (TODO optimize)
-    // a hole is any space below us with a lesser density
-    // prevents equidistance stuck state
-    let starting_side = if ctx.seqno_parity == 0 { 1 } else { -1 };
-    for i in 0..20 {
-        let side = if i % 2 == 0 {
-            starting_side
-        } else {
-            -starting_side
-        };
-
-        let offset = side * (1 + i / 2);
-        let hole_target = ctx.get_cell(offset, -1);
-        if let Some(target) = hole_target
-            && target.material.def().density < ctx.material.density
-        {
-            // we identified a hole and we know that the space on this side is open
-            // move toward the hole
-            // new_target.flags = new_target.flags ^ 0b1;
-            ctx.candidates_swap(&[(side, 0)]);
-            return;
-        }
-    }
-
-    // we didn't find a hole, so just move "randomly" on the same surface
-    // TODO when to settle?
-    let target_x = if !can_move_left {
-        1
-    } else if !can_move_right {
-        -1
-    } else if ctx.seqno_parity % 2 == 1 {
-        1
-    } else {
-        -1
-    };
-
-    ctx.candidates_swap(&[(target_x, 0)]);
+    if ctx.rng.random_range(0.0..1.0) > 0.8
+        && ctx.candidates_swap(&[(-1 + ctx.seqno_parity as i32 * 2, 0)])
+    {}
 }