diff --git a/simulator-sketch.js b/simulator-sketch.js
index 3a8b91e..f646bc8 100644
--- a/simulator-sketch.js
+++ b/simulator-sketch.js
@@ -33,6 +33,28 @@ function CPU(mem) {
       this.acc = this.memory[addr];
       this.instructionPointer = this.instructionPointer += 1;
     },
+    add_lit: (lit) => {
+      console.log("ADD lit");
+      if ( (this.acc + lit) > 15 ) { this.carryFlag = 1; }
+      this.acc = (this.acc + lit % 15);
+      this.instructionPointer = this.instructionPointer += 1;
+    },
+    add_addr: (addr) => {
+      console.log("ADD addr");
+      if ( (this.acc + this.memory[addr]) > 15 ) { this.carryFlag = 1; }
+      this.acc = (this.acc + this.memory[addr] % 15);
+      this.instructionPointer = this.instructionPointer += 1;
+    },
+    sub_lit: (lit) => { // TODO: carry flag
+      console.log("SUB lit");
+      this.acc = this.acc - lit;
+      this.instructionPointer = this.instructionPointer += 1;
+    },
+    sub_addr: (addr) => { // TODO: carry flag
+      console.log("SUB addr");
+      this.acc = this.acc - this.memory[addr];
+      this.instructionPointer = this.instructionPointer += 1;
+    },
   };
 
   log_debug_state = () => {
@@ -71,6 +93,22 @@ function CPU(mem) {
       case 4:
         this.instructions.load_addr(arg);
         break;
+
+      case 5:
+        this.instructions.add_lit(arg);
+        break;
+
+      case 6:
+        this.instructions.add_addr(arg);
+        break;
+
+      case 7:
+        this.instructions.sub_lit(arg);
+        break;
+
+      case 8:
+        this.instructions.sub_addr(arg);
+        break;
       
       default:
         console.error( `Invalid opcode: ${opcode} with argument ${arg}` );
@@ -100,10 +138,6 @@ function CPU(mem) {
 };
 
 // UNIMPLEMENTED
-  let add_lit = function(lit) { return; }
-  let add_addr = function(addr) { return; }
-  let subtract_lit = function(lit) { return; }
-  let subtract_addr = function(addr) { return; }
   let hop_lit = function(lit) { return; }
   let hop_addr = function(addr) { return; }
   let jump_lit = function(lit) { return; }
@@ -119,13 +153,29 @@ let halt_and_catch_fire = [
   [1, 0],
 ];
 
-let basic_test = [
+let test_lda_sto = [
   [3, 8], // LDA lit
   [1, 5], // STO lit
   [4, 5], // LDA addr
   [2, 6], // STO addr
   [0, 0], // END
 ];
+// let comp = new CPU(test_lda_sto);
+// comp.run_program();
 
-let comp = new CPU(basic_test);
+let test_add_sub_nocarry = [
+  [5, 6], // ADD lit  ... acc = 6
+  [7, 1], // SUB lit  ... acc = 5
+  [1, 8], // STO lit  ... mem[8] = 5
+  [6, 8], // ADD addr ... acc = 10
+  [8, 8], // SUB addr ... acc = 5
+  [0, 0], // END
+]
+
+let test_add_sub = [
+  [5, 26], // ADD lit
+  [0, 0], // END
+]
+
+let comp = new CPU(test_add_sub);
 comp.run_program();
\ No newline at end of file