diff --git a/lib/utils.js b/lib/utils.js
new file mode 100644
index 0000000..2d9bd4f
--- /dev/null
+++ b/lib/utils.js
@@ -0,0 +1,65 @@
+'use strict';
+
+exports.and = () => {
+  let state = 0; // idle
+  let total = 0;
+  let start = 0;
+
+  return {
+    onA: (time, cmd) => {
+      switch(state) {
+      case 0: if (cmd === 15) { state = 1; } break;
+      case 1: if (cmd === 14) { state = 0; } break;
+      case 2: if (cmd === 15) { state = 3; start = time; } break;
+      case 3: if (cmd === 14) { state = 2; total += (time - start); start = 0; } break;
+      default: throw new Error();
+      }
+    },
+    onNotA: (time, cmd) => {
+      switch(state) {
+      case 0: if (cmd === 14) { state = 1; } break;
+      case 1: if (cmd === 15) { state = 0; } break;
+      case 2: if (cmd === 14) { state = 3; start = time; } break;
+      case 3: if (cmd === 15) { state = 2; total += (time - start); start = 0; } break;
+      default: throw new Error();
+      }
+    },
+    onB: (time, cmd) => {
+      switch(state) {
+      case 0: if (cmd === 15) { state = 2; } break;
+      case 1: if (cmd === 15) { state = 3; start = time; } break;
+      case 2: if (cmd === 14) { state = 0; } break;
+      case 3: if (cmd === 14) { state = 1; total += (time - start); start = 0; } break;
+      default: throw new Error();
+      }
+    },
+    onNotB: (time, cmd) => {
+      switch(state) {
+      case 0: if (cmd === 14) { state = 2; } break;
+      case 1: if (cmd === 14) { state = 3; start = time; } break;
+      case 2: if (cmd === 15) { state = 0; } break;
+      case 3: if (cmd === 15) { state = 1; total += (time - start); start = 0; } break;
+      default: throw new Error();
+      }
+    },
+    time: () => total + start
+  };
+};
+
+
+exports.activity = skip => {
+  let start = 0;
+  let stop = 0;
+  return {
+    on: time => {
+      if (time > skip) {
+        if (start == 0) {
+          start = time;
+        } else {
+          stop = time;
+        }
+      }
+    },
+    time: () => stop - start
+  };
+};