diff --git a/crates-ptx/Cargo.lock b/crates-ptx/Cargo.lock
index 705a03f..475f6bb 100644
--- a/crates-ptx/Cargo.lock
+++ b/crates-ptx/Cargo.lock
@@ -345,9 +345,9 @@ checksum = "e53debba6bda7a793e5f99b8dacf19e626084f525f7829104ba9898f367d85ff"
 
 [[package]]
 name = "nalgebra"
-version = "0.32.1"
+version = "0.32.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f6515c882ebfddccaa73ead7320ca28036c4bc84c9bcca3cc0cbba8efe89223a"
+checksum = "307ed9b18cc2423f29e83f84fd23a8e73628727990181f18641a8b5dc2ab1caa"
 dependencies = [
  "approx",
  "bytemuck",
@@ -363,9 +363,9 @@ dependencies = [
 
 [[package]]
 name = "nalgebra-macros"
-version = "0.2.0"
+version = "0.2.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d232c68884c0c99810a5a4d333ef7e47689cfd0edc85efc9e54e1e6bf5212766"
+checksum = "91761aed67d03ad966ef783ae962ef9bbaca728d2dd7ceb7939ec110fffad998"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -482,9 +482,9 @@ checksum = "b15813163c1d831bf4a13c3610c05c0d03b39feb07f7e09fa234dac9b15aaf39"
 
 [[package]]
 name = "parry2d"
-version = "0.13.0"
+version = "0.13.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "a2342b33d77a0393879b1b85eac2a30cc4b36d10b30e111f55a5e9280cf5eb87"
+checksum = "104ae65232e20477a98f9f1e75ca9850eae24a2ea846a2b1a0af03ad752136ce"
 dependencies = [
  "approx",
  "arrayvec",
@@ -502,9 +502,9 @@ dependencies = [
 
 [[package]]
 name = "parry3d"
-version = "0.13.0"
+version = "0.13.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d2852a4cf8f65177e6f3755a725fdc0a433cca4fa6a97a07ae8c8abd7a4b52ea"
+checksum = "b55dc0e6db79bddbc5fd583569f7356cdcc63e1e9b2b93a9ab70dd8e717160e0"
 dependencies = [
  "approx",
  "arrayvec",
@@ -740,7 +740,7 @@ version = "0.4.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "bfa0f585226d2e68097d4f95d113b15b83a82e819ab25717ec0590d9584ef366"
 dependencies = [
- "semver 1.0.16",
+ "semver 1.0.20",
 ]
 
 [[package]]
@@ -769,9 +769,9 @@ dependencies = [
 
 [[package]]
 name = "semver"
-version = "1.0.16"
+version = "1.0.20"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "58bc9567378fc7690d6b2addae4e60ac2eeea07becb2c64b9f218b53865cba2a"
+checksum = "836fa6a3e1e547f9a2c4040802ec865b5d85f4014efe00555d7090a3dcaa1090"
 
 [[package]]
 name = "semver-parser"
@@ -821,9 +821,9 @@ dependencies = [
 
 [[package]]
 name = "simba"
-version = "0.8.0"
+version = "0.8.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "50582927ed6f77e4ac020c057f37a268fc6aebc29225050365aacbb9deeeddc4"
+checksum = "061507c94fc6ab4ba1c9a0305018408e312e17c041eb63bef8aa726fa33aceae"
 dependencies = [
  "approx",
  "cuda_std",
@@ -1020,9 +1020,9 @@ checksum = "accd4ea62f7bb7a82fe23066fb0957d48ef677f6eeb8215f372f52e48bb32426"
 
 [[package]]
 name = "vek"
-version = "0.15.9"
+version = "0.15.10"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "02eeed9a6ab91448e2aea59ffa21e644e22dc373ab0a187ac34ada660c2cb9de"
+checksum = "8085882662f9bc47fc8b0cdafa5e19df8f592f650c02b9083da8d45ac9eebd17"
 dependencies = [
  "approx",
  "num-integer",
diff --git a/src_kernels/cuda/grid_update.rs b/src_kernels/cuda/grid_update.rs
index 9984a35..20d6ab4 100644
--- a/src_kernels/cuda/grid_update.rs
+++ b/src_kernels/cuda/grid_update.rs
@@ -108,11 +108,12 @@ fn update_single_cell(
                     }
                 }
                 BoundaryHandling::Friction | BoundaryHandling::FrictionZUp => {
-                    if let Some((mut normal, dist)) =
+                    if let Some((mut normal, mut dist)) =
                         Unit::try_new_and_get(cell.projection_scaled_dir, 1.0e-5)
                     {
                         if is_inside {
                             normal = -normal;
+                            dist = 0.0;
                         }
 
                         #[cfg(feature = "dim2")]
@@ -125,25 +126,29 @@ fn update_single_cell(
 
                         if apply_friction {
                             let normal_vel = cell_velocity.dot(&normal);
+                            let dist_with_margin = (dist - cell_width * 0.5).max(0.0);
 
-                            if normal_vel < 0.0 {
-                                let dist_with_margin = dist - cell_width;
-                                if is_inside || dist_with_margin <= 0.0 {
-                                    let tangent_vel =
-                                        cell_velocity - normal_vel * normal.into_inner();
-                                    let tangent_vel_norm = tangent_vel.norm();
-
-                                    cell_velocity = tangent_vel;
-
-                                    if tangent_vel_norm > 1.0e-10 {
-                                        let friction = collider.friction;
-                                        cell_velocity = tangent_vel / tangent_vel_norm
-                                            * (tangent_vel_norm + normal_vel * friction).max(0.0);
-                                    }
-                                } else if -normal_vel * dt > dist_with_margin {
-                                    cell_velocity -=
-                                        (dist_with_margin / dt + normal_vel) * normal.into_inner();
-                                }
+                            if -normal_vel * dt > dist_with_margin {
+                                // NOTE: if we enter this code, normal_vel is negative.
+                                let tangent_vel = cell_velocity - normal_vel * normal.into_inner();
+                                let tangent_vel_norm = tangent_vel.norm();
+
+                                let new_normal_vel = normal_vel.max(-dist_with_margin / dt);
+
+                                // NOTE: removed_normal_vel is always positive.
+                                let removed_normal_vel = new_normal_vel - normal_vel;
+
+                                let new_tangent_vel = if tangent_vel_norm > 1.0e-6 {
+                                    tangent_vel / tangent_vel_norm
+                                        * (tangent_vel_norm
+                                            - removed_normal_vel * collider.friction)
+                                            .max(0.0)
+                                } else {
+                                    Vector::zeros()
+                                };
+
+                                cell_velocity =
+                                    new_normal_vel * normal.into_inner() + new_tangent_vel;
                             }
                         }
                     }