diff --git a/assembler.js b/assembler.js
index 394b610..63f9cc4 100644
--- a/assembler.js
+++ b/assembler.js
@@ -38,14 +38,6 @@ const mnemonics2opcodes = {
   nop: { direct: 15, indirect: 15 },
 };
 
-/**
- * @param {string} s
- * @returns {boolean}
- **/
-function startsWithPointerToIP(s) {
-  return stripWhitespaceFromEnds(s).startsWith(ASM_IP_LABEL);
-}
-
 
 /**
  * @typedef {('code'|'comment'|'blank')} SourceLineType
@@ -91,7 +83,7 @@ function preparseSourceCode(source) {
     };
 
     if (info.type === 'code') {
-      const op_arg_array = line.split(/\s+/); // split line into an array of [op, arg]
+      const op_arg_array = info.sanitized.split(/\s+/); // split line into an array of [op, arg]
       if (op_arg_array[0] !== 'undefined') {
         info.operation = op_arg_array[0];
       }
@@ -109,19 +101,67 @@ function preparseSourceCode(source) {
  * @param {string} arg
  * @returns {number}
  **/
-function parseNumericOperand(arg) {
+function decodeNumericOp(arg) {
   if (arg.startsWith("$")) return hex2num(arg.replace("$", ""));
   return parseInt(arg);
 }
 
-      // DECODE!
-      const op = mnemonics2opcodes[opName][addressingMode]; // FIXME rename
 
-      machineCode.push(op);
-      machineCode.push(arg_num);
-      dbg(3, `IP: $${num2hex(IP)}, new code: $${num2hex(op)} $${num2hex(arg_num)}`);
-      IP += 2;
-      dbgGroupEnd(1, 'Input line');
+/**
+ * @param {string} op
+ * @param {object} labels // TODO
+ * @param {number} IP
+ * @returns {Array<string>} - array of labels
+ **/
+function handleLabelDefinition(op, IP, labels) {
+  let label = op.substring(1); // strip label prefix
+
+  if (label in labels) {
+    labels[label].pointsToByte = IP;
+  } else {
+    labels[label] = {
+      pointsToByte: IP,
+      bytesToReplace: [],
+    };
+  }
+  dbg(2, `pointsToByte: ${labels[label].pointsToByte}`);
+  dbg(2, `bytesToReplace: ${labels[label].bytesToReplace}`);
+  dbg(3, `IP: $${num2hex(IP)}, new code: none`);
+  dbgGroupEnd(1, 'Input line');
+  return labels;
+}
+
+/**
+ * @param {string} op
+ * @param {string} arg
+ * @param {number} IP
+ * @returns {Array<string>} - array of constants
+ **/
+function handleConstantDefinitions(op, arg, IP, constants) {
+  let constantName = op.substring(1); // strip '>'
+  let constantValue = arg;
+  if (constantValue === ASM_IP_LABEL) {
+    constantValue = IP.toString();
+  }
+  constants[constantName] = constantValue;
+  dbg(2, `constants:`);
+  dbg(2, constants);
+  return constants;
+}
+
+/**
+ * @param {SourceLineInfo} line
+ * @returns {Object}
+ **/
+function assembleMnemonicsWithOptionalArgs(line, assemblerState) {
+  if (mnemonicsWithOptionalArgs.indexOf(line.operation) < 0) {
+    console.error(`Missing opcode for line ${line.number}: ${line.source}`);
+    throw new Error("Missing opcode");
+  }
+  let opcode = decodeNumericOp(line.operation);
+  let operand = line.argument !== null ? decodeNumericOp(line.argument) : 0;
+  return [opcode, operand];
+}
 
 
 /**
@@ -134,18 +174,7 @@ function parseNumericOperand(arg) {
  * @return TODO
  **/
 function decodeInstructions(source) {
-  // WIP: everything broken
-  // - just finished writing `splitCodeFromComments`
-  // - plan:
-  //    - use that to pre-load debugInfo array
-  //    - and to check if the first code-line is `*`
-  // so currently i'm implementing 2 entangled features:
-  //    1. check if first line * and set IP
-  //    2. return debug data along with machine code
-
   let lines = preparseSourceCode(source);
-  console.log(lines);
-
 
   // Figure out where to start assembly...
 
@@ -175,7 +204,7 @@ function decodeInstructions(source) {
   let labels = {};
   let constants = {};
 
-  // Decode line by line
+  // Decode line by line...
   for (let i = 0; i < lines.length; i++) {
     let line = lines[0];
     if (line.type === 'code') {
@@ -185,73 +214,42 @@ function decodeInstructions(source) {
         const arg = line.argument;
       }
 
-      /** @type {{op: (number | null), arg: (number|null)}} **/
-      let assembledLine = {
-        op: null,
-        arg: null
-      };
 
-      /** @type {'direct'|'indirect'} **/
-      let addressingMode = 'direct';
+      // *** Decode special operations ***
 
       // Opcodes - Handle label definitions
       if (op.startsWith(ASM_LABEL_PREFIX)) {
-        let label = op.substring(1); // strip label prefix
-
-        if (label in labels) {
-          labels[label].pointsToByte = IP;
-        } else {
-          labels[label] = {
-            pointsToByte: IP,
-            bytesToReplace: [],
-          };
-        }
-        dbg(2, `pointsToByte: ${labels[label].pointsToByte}`);
-        dbg(2, `bytesToReplace: ${labels[label].bytesToReplace}`);
-        dbg(3, `IP: $${num2hex(IP)}, new code: none`);
-        dbgGroupEnd(1, 'Input line');
-        continue;
-      }
-
-      // let op_arg_array = line.split(/\s+/); // split line into an array of [op, arg]
-      // let opName = op_arg_array[0].toLowerCase();
-      // let arg_str = op_arg_array[1];
-      // let arg_num = null;
-
-      // Opcodes - Handle setting value of IP
-      if (startsWithPointerToIP(op)) {
-        dbg(3, 'CHANGING IP');
-        IP = parseInt(arg);
+        labels = handleLabelDefinition(op, IP, labels);
         continue;
       }
 
       // Opcodes - Handle constant definitions
       if (op.startsWith(ASM_CONSTANT_PREFIX)) {
-        let constantName = op.substring(1); // strip '>'
-        let constantValue = arg;
-        if (constantValue === ASM_IP_LABEL) {
-          constantValue = IP.toString();
-        }
-        constants[constantName] = constantValue;
-        dbg(2, `constants:`);
-        dbg(2, constants);
+        constants = handleConstantDefinitions(op, arg, IP, constants);
         continue;
       }
 
-      // Opcodes - Handle mnemonics without operands (eg END) ...
-      if (arg === null) {
-        if (mnemonicsWithOptionalArgs.indexOf(op) < 0) {
-          console.error(`Missing opcode for line ${line.number}: ${line.source}`);
-          throw new Error("Missing opcode");
-        }
-        assembledLine.arg = 0;
+      // Opcodes - Handle setting value of IP
+      if (op.startsWith(ASM_IP_LABEL)) {
+        IP = parseInt(arg);
+        continue;
+      }
+
+      // *** Decode regular operations ***
+
+      /** @type {number|null} decodedOp **/
+      let decodedOp = null;
+
+      /** @type {number|null} decodedArg **/
+      let decodedArg = null;
+
+      /** @typedef {'direct'|'indirect'} AddressingMode **/
+      let addressingMode = 'direct';
 
 
       // Operands - Handle references to labels
-      } else if (arg.startsWith(ASM_LABEL_PREFIX)) {
-        let label = arg.substring(1); // strip label prefix
-        assembledLine.arg = 0;
-
+      if (arg !== null && arg.startsWith(ASM_LABEL_PREFIX)) {
+        let label = line.argument.substring(1); // strip label prefix
         if (label in labels) {
           dbg(1, `'${label}' already in labels object`);
           labels[label].bytesToReplace.push(IP + 1);
@@ -263,43 +261,56 @@ function decodeInstructions(source) {
         }
         dbg(2, `pointsToByte: ${labels[label].pointsToByte}`);
         dbg(2, `bytesToReplace: ${labels[label].bytesToReplace}`);
+        let code = [decodeNumericOp(line.operation), 0] // Return 0 for operand for now -- we'll replace it later
+      }
       
       // Operands - Handle references to the Instruction Pointer
-      } else if (arg.toLowerCase() === ASM_IP_LABEL) {
+      if (arg !== null && arg === ASM_IP_LABEL) {
         dbg(2, `operand references current address`);
-        assembledLine.arg = IP;
-        dbg(2, `arg_num: ${num2hex(assembledLine.arg)}`);
+        decodedArg = IP;
+        dbg(2, `arg_num: ${num2hex(decodedArg)}`);
+      }
 
       // Operands - Handle references to constants
-      } else if (arg.startsWith(ASM_CONSTANT_PREFIX)) {
+      if (arg !== null && arg.startsWith(ASM_CONSTANT_PREFIX)) {
         dbg(2, `operand references '${arg}'`);
-        assembledLine.arg = constants[arg.substring(1)]; // substring(1) strips '>'
+        decodedArg = constants[arg.substring(1)]; // substring(1) strips '>'
+      }
       
       // Operands - Handle references to constants in indirect mode
-      } else if (arg.startsWith(`(${ASM_CONSTANT_PREFIX}`)) {
+      if (arg !== null && arg.startsWith(`(${ASM_CONSTANT_PREFIX}`)) {
         addressingMode = "indirect";
         dbg(2, `IND - operand references '${arg}'`);
         let constTemp = arg.replace(`(${ASM_CONSTANT_PREFIX}`, "").replace(")", "");
-        assembledLine.arg = constants[constTemp];
+        decodedArg = constants[constTemp];
+      }
 
       // Operands - Handle indirect expressions
-      } else if (arg.startsWith("(")) {
+      if (arg !== null && arg.startsWith("(")) {
         addressingMode = "indirect";
-        assembledLine.arg = arg.replace("(", "").replace(")", "");
+        let indyTemp = arg.replace("(", "").replace(")", "");
+        decodedArg = decodeNumericOp(indyTemp);
       }
 
-      // Operands - Handle numeric operands
-      if (arg_num === null) {
-        if (arg_str.startsWith("$")) {
-          // Handle hex
-          arg_str = arg_str.replace("$", "");
-          arg_num = hex2num(arg_str);
-        } else {
-          // Accept decimal i guess
-          arg_num = parseInt(arg_str);
+      // Opcodes - Handle mnemonics without operands (eg END)
+      if (arg === null) {
+        if (mnemonicsWithOptionalArgs.indexOf(line.operation) < 0) {
+          console.error(`Missing opcode for line ${line.number}: ${line.source}`);
+          throw new Error("Missing opcode");
         }
+        decodedOp = decodeNumericOp(line.operation);
+        decodedArg = line.argument !== null ? decodeNumericOp(line.argument) : 0;
       }
 
+      if (decodedOp === null) {
+        decodedOp = mnemonics2opcodes[line.operation][addressingMode];
+      }
+
+      machineCode.push(decodedOp);
+      machineCode.push(decodedArg);
+      dbg(3, `IP: $${num2hex(IP)}, new code: $${num2hex(decodedOp)} $${num2hex(decodedArg)}`);
+      IP += 2;
+      dbgGroupEnd(1, 'Input line');
     };
   }