diff --git a/calt.js b/calt.js
new file mode 100644
index 0000000..4d0a9ba
--- /dev/null
+++ b/calt.js
@@ -0,0 +1,66 @@
+const fs = require('fs');
+
+const rules = [
+  ,
+  `
+lookup 1 {
+  sub 1 by glyph;
+} 1;`,
+  `
+lookup 1_2 {
+  ignore sub 1 1' 2;
+  ignore sub 1' 2 2;
+  sub 1.spacer 2' by glyph;
+  sub 1'       2  by 1.spacer;
+} 1_2;`,
+  `
+lookup 1_2_3 {
+  ignore sub 1 1' 2 3;
+  ignore sub 1' 2 3 3;
+  sub 1.spacer 2.spacer 3' by glyph;
+  sub 1.spacer 2'       3  by 2.spacer;
+  sub 1'       2        3  by 1.spacer;
+} 1_2_3;`,
+  `
+lookup 1_2_3_4 {
+  ignore sub 1 1' 2 3 4;
+  ignore sub 1' 2 3 4 4;
+  sub 1.spacer 2.spacer 3.spacer 4' by glyph;
+  sub 1.spacer 2.spacer 3'       4  by 3.spacer;
+  sub 1.spacer 2'       3        4  by 2.spacer;
+  sub 1'       2        3        4  by 1.spacer;
+} 1_2_3_4;`,
+];
+
+const gencalt = (ligatures) => {
+  let calt = 'feature calt {\n';
+  const ligs = {};
+  console.log(ligatures);
+
+  ligatures
+    .filter((l) => !!l.name.match(/\.liga$/) || l.name !== l.glyph)
+    .map((l) => l.glyph)
+    .sort((a, b) => {
+      const length = b.split('_').length - a.split('_').length;
+      if (length !== 0) return length;
+      return a < b ? -1 : 1;
+    })
+    .forEach((g) => {
+      g.split('.')
+        .slice(0, 1)
+        .forEach((l) => {
+          if (ligs[l]) return;
+          ligs[l] = true;
+          const c = l.split('_');
+          let rule = rules[c.length];
+          rule = rule
+            .replace(/\d/g, (m) => c[parseInt(m) - 1])
+            .replace(/glyph/g, g);
+          calt += rule + '\n';
+        });
+    });
+
+  return calt + '\n} calt;\n';
+};
+
+exports.gencalt = gencalt;
diff --git a/features/.gitignore b/features/.gitignore
new file mode 100644
index 0000000..78837e8
--- /dev/null
+++ b/features/.gitignore
@@ -0,0 +1 @@
+calt.fea