diff --git a/creature.go b/creature.go
index 72b2e68..719f25e 100644
--- a/creature.go
+++ b/creature.go
@@ -20,6 +20,26 @@ type Machine struct {
 // machine will halt execution if true is returned.
 type MachineFunction func(machine *Machine) (stop bool)
 
+// All supported opcodes
+const (
+	PUSH = 0x0
+	POP  = 0x1
+	LOAD = 0x2
+	STOR = 0x3
+	ADD  = 0x4
+	SUB  = 0x5
+	MUL  = 0x6
+	DIV  = 0x7
+	EQ   = 0x8
+	GT   = 0x9
+	LT   = 0xa
+	NEQ  = 0xb
+	MOD  = 0xc
+	HALT = 0xd
+	JMP  = 0xe
+	CAL  = 0xf
+)
+
 // Error is an error type that can be returned from the machine's methods if
 // they experience problems.
 type Error int
@@ -62,45 +82,37 @@ func (machine *Machine) Execute(offset int) (err error) {
 
 	for machine.counter < len(machine.Program) {
 		switch machine.instruction() {
-		case 0x0:
-			// PUSH
+		case PUSH:
 			// push the next word in program memory onto the stack
 			machine.counter++
 			machine.Push(machine.instruction())
 
-		case 0x1:
-			// POP
+		case POP:
 			// pop the top word off of the stack, and discard it
 			machine.Pop()
 
-		case 0x2:
-			// LOAD
+		case LOAD:
 			// push the word at an address onto the stack
 			machine.Push(machine.Peek(machine.Pop()))
 
-		case 0x3:
-			// STOR
+		case STOR:
 			// store a word at an address
 			machine.Poke(machine.Pop(), machine.Pop())
 
-		case 0x4:
-			// ADD
+		case ADD:
 			// adds the last two words on the stack
 			machine.Push(machine.Pop() + machine.Pop())
 
-		case 0x5:
-			// SUB
+		case SUB:
 			// subtracts the second to last word on the stack from
 			// the last word on the stack
 			machine.Push(machine.Pop() - machine.Pop())
 
-		case 0x6:
-			// MUL
+		case MUL:
 			// multiplies the last two words on the stack
 			machine.Push(machine.Pop() * machine.Pop())
 
-		case 0x7:
-			// DIV
+		case DIV:
 			// divides the last word on the stack by the second to
 			// last word on the stack
 			left  := machine.Pop()
@@ -111,8 +123,7 @@ func (machine *Machine) Execute(offset int) (err error) {
 			}
 			machine.Push(left / right)
 
-		case 0x8:
-			// EQ
+		case EQ:
 			// checks if the last two words on the stack are equal
 			equal := 0
 			if machine.Pop() == machine.Pop() {
@@ -120,8 +131,7 @@ func (machine *Machine) Execute(offset int) (err error) {
 			}
 			machine.Push(equal)
 
-		case 0x9:
-			// GT
+		case GT:
 			// checks if the last word on the stack is greater than
 			// the second to last word on the stack
 			greater := 0
@@ -130,8 +140,7 @@ func (machine *Machine) Execute(offset int) (err error) {
 			}
 			machine.Push(greater)
 
-		case 0xa:
-			// LT
+		case LT:
 			// checks if the last word on the stack is less than the
 			// second to last word on the stack
 			less := 0
@@ -140,8 +149,7 @@ func (machine *Machine) Execute(offset int) (err error) {
 			}
 			machine.Push(less)
 
-		case 0xb:
-			// NEQ
+		case NEQ:
 			// checks if the last two words on the stack are not
 			// equal
 			notEqual := 0
@@ -150,19 +158,16 @@ func (machine *Machine) Execute(offset int) (err error) {
 			}
 			machine.Push(notEqual)
 
-		case 0xc:
-			// MOD
+		case MOD:
 			// performs a modulo operation of the second to last
 			// word on the stack to the last word on the stack
 			machine.Push(machine.Pop() % machine.Pop())
 
-		case 0xd:
-			// HALT
+		case HALT:
 			// stops execution
 			return
 
-		case 0xe:
-			// JMP
+		case JMP:
 			// jump to the address specified by the last word on the
 			// stack if the second to last word on the stack is
 			// nonzero
@@ -171,8 +176,7 @@ func (machine *Machine) Execute(offset int) (err error) {
 				machine.counter = jumpTo - 1
 			}
 
-		case 0xf:
-			// CAL
+		case CAL:
 			// call an implementation-defined subroutine, with the
 			// id specified by the last word on the stack. this may
 			// push and pop various things from the stack
diff --git a/creature_test.go b/creature_test.go
index a7055f9..a3cb62d 100644
--- a/creature_test.go
+++ b/creature_test.go
@@ -16,7 +16,7 @@ func runMachineTest(program []int, test *testing.T) (machine *Machine) {
 
 func TestPush(test *testing.T) {
 	machine := runMachineTest ([]int {
-		0x0, 654,
+		PUSH, 654,
 	}, test)
 	
 	result := machine.Pop()
@@ -30,21 +30,21 @@ func TestPush(test *testing.T) {
 
 func TestArithmetic(test *testing.T) {
 	machine := runMachineTest([]int {
-		0x0, 2,
-		0x0, 3,
-		0x4,
+		PUSH, 2,
+		PUSH, 3,
+		ADD,
 		
-		0x0, 10,
-		0x0, 4,
-		0x5,
+		PUSH, 10,
+		PUSH, 4,
+		SUB,
 		
-		0x0, 7,
-		0x0, 2,
-		0x6,
+		PUSH, 7,
+		PUSH, 2,
+		MUL,
 		
-		0x0, 12,
-		0x0, 3,
-		0x7,
+		PUSH, 12,
+		PUSH, 3,
+		DIV,
 	}, test)
 
 	addResult := machine.Pop()