diff --git a/src/falling_sand/rules.rs b/src/falling_sand/rules.rs
index 94625c8..d7febc6 100644
--- a/src/falling_sand/rules.rs
+++ b/src/falling_sand/rules.rs
@@ -2,6 +2,37 @@ use bevy::{ecs::system::Resource, utils::HashMap};
 
 use super::Element;
 
+struct RuleConfig {
+    element_groups: Vec<Vec<Element>>,
+    rules: Vec<([usize; 4], [usize; 4])>,
+}
+
+impl RuleConfig {
+    fn compile(&self) -> HashMap<u32, u32> {
+        let mut rules = HashMap::new();
+        for i in 0..self.rules.len() {
+            let rule = self.rules[i];
+
+            let i0 = &self.element_groups[rule.0[0]];
+            let i1 = &self.element_groups[rule.0[1]];
+            let i2 = &self.element_groups[rule.0[2]];
+            let i3 = &self.element_groups[rule.0[3]];
+
+            let o0 = &self.element_groups[rule.1[0]];
+            let o1 = &self.element_groups[rule.1[1]];
+            let o2 = &self.element_groups[rule.1[2]];
+            let o3 = &self.element_groups[rule.1[3]];
+
+            // !HACK: Assume element groups are length 1 for now!
+            let input = to_rule_state((i0[0], i1[0], i2[0], i3[0]));
+            let output = to_rule_state((o0[0], o1[0], o2[0], o3[0]));
+            rules.insert(input, output);
+        }
+
+        rules
+    }
+}
+
 #[derive(Resource)]
 pub struct FallingSandRules {
     rules: HashMap<u32, u32>,
@@ -10,46 +41,23 @@ pub struct FallingSandRules {
 impl Default for FallingSandRules {
     fn default() -> Self {
         // Pre-computed air-sand rules
-        Self {
-            rules: HashMap::from([
-                gen_rule(
-                    (Element::Air, Element::Sand, Element::Air, Element::Air),
-                    (Element::Air, Element::Air, Element::Air, Element::Sand),
-                ),
-                gen_rule(
-                    (Element::Air, Element::Sand, Element::Air, Element::Sand),
-                    (Element::Air, Element::Air, Element::Sand, Element::Sand),
-                ),
-                gen_rule(
-                    (Element::Air, Element::Sand, Element::Sand, Element::Air),
-                    (Element::Air, Element::Air, Element::Sand, Element::Sand),
-                ),
-                gen_rule(
-                    (Element::Sand, Element::Air, Element::Air, Element::Air),
-                    (Element::Air, Element::Air, Element::Sand, Element::Air),
-                ),
-                gen_rule(
-                    (Element::Sand, Element::Air, Element::Air, Element::Sand),
-                    (Element::Air, Element::Air, Element::Sand, Element::Sand),
-                ),
-                gen_rule(
-                    (Element::Sand, Element::Air, Element::Sand, Element::Air),
-                    (Element::Air, Element::Air, Element::Sand, Element::Sand),
-                ),
-                gen_rule(
-                    (Element::Sand, Element::Sand, Element::Air, Element::Air),
-                    (Element::Air, Element::Air, Element::Sand, Element::Sand),
-                ),
-                gen_rule(
-                    (Element::Sand, Element::Sand, Element::Air, Element::Sand),
-                    (Element::Air, Element::Sand, Element::Sand, Element::Sand),
-                ),
-                gen_rule(
-                    (Element::Sand, Element::Sand, Element::Sand, Element::Air),
-                    (Element::Sand, Element::Air, Element::Sand, Element::Sand),
-                ),
-            ]),
-        }
+        let rule_config = RuleConfig {
+            element_groups: vec![vec![Element::Air], vec![Element::Sand]],
+            rules: vec![
+                ([0, 1, 0, 0], [0, 0, 0, 1]),
+                ([0, 1, 0, 1], [0, 0, 1, 1]),
+                ([0, 1, 1, 0], [0, 0, 1, 1]),
+                ([1, 0, 0, 0], [0, 0, 1, 0]),
+                ([1, 0, 0, 1], [0, 0, 1, 1]),
+                ([1, 0, 1, 0], [0, 0, 1, 1]),
+                ([1, 1, 0, 0], [0, 0, 1, 1]),
+                ([1, 1, 0, 1], [0, 1, 1, 1]),
+                ([1, 1, 1, 0], [1, 0, 1, 1]),
+            ],
+        };
+        let rules = rule_config.compile();
+
+        Self { rules }
     }
 }