diff --git a/src/step.wgsl b/src/step.wgsl
index 515aa78..f4ba49a 100644
--- a/src/step.wgsl
+++ b/src/step.wgsl
@@ -34,10 +34,23 @@ fn on_fragment(in: Varying) -> @location(0) vec4u {
 		}
 	}
 	n -= state;
-	return vec4(rule(state.x, n.x), rule(state.y, n.y), rule(state.z, n.z), rule(state.w, n.w));
+
+	let z = daynight(state.z, n.z);
+	let px = life(state.x, n.x);
+	let nx = 1u - life(1u - state.x, 8u - n.x);
+	let x = z * px + (1u - z) * nx;
+	return vec4(x, 0, z, 0u);
 }
 
-fn rule(state: u32, n: u32) -> u32{
+fn life(state: u32, n: u32) -> u32{
+	switch (n) {
+	case 2u: { return state; }
+	case 3u: { return 1u; }
+	default: { return 0u; }
+	}
+}
+
+fn daynight(state: u32, n: u32) -> u32{
 	switch (n) {
 	case 3u: { return 1u; }
 	case 4u: { return state; }