diff --git a/src/go.mod b/src/go.mod
new file mode 100644
index 0000000..63f180d
--- /dev/null
+++ b/src/go.mod
@@ -0,0 +1,5 @@
+module github.com/k3y0708/otter
+
+go 1.19
+
+require github.com/carmark/pseudo-terminal-go v0.0.0-20151106093136-5a48ae24c6f5 // indirect
diff --git a/src/go.sum b/src/go.sum
new file mode 100644
index 0000000..cec6881
--- /dev/null
+++ b/src/go.sum
@@ -0,0 +1,2 @@
+github.com/carmark/pseudo-terminal-go v0.0.0-20151106093136-5a48ae24c6f5 h1:WsxAWarPn1PKpBPSzGCH5qLbcioqdxsXuYIwc+RYz9U=
+github.com/carmark/pseudo-terminal-go v0.0.0-20151106093136-5a48ae24c6f5/go.mod h1:8Qkync7rscOMM34525Dcy8RQ/LUCtXt5IagpNsEMRKU=
diff --git a/src/main.go b/src/main.go
new file mode 100644
index 0000000..87253ea
--- /dev/null
+++ b/src/main.go
@@ -0,0 +1,282 @@
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+	"os"
+	"os/exec"
+	"os/user"
+	"strings"
+
+	"github.com/k3y0708/otter/terminal"
+)
+
+const (
+	Prompt       = "otter> "
+	OtterHistory = ".otterhistory"
+	OtterRC      = ".otterrc"
+)
+
+func executeCommand(cmd string, args []string) {
+	// Execute command
+	switch cmd {
+	case "exit":
+		os.Exit(0)
+	case "source":
+		if len(args) == 0 {
+			os.Stderr.WriteString("source: missing file operand\n")
+			return
+		}
+
+		// Check if file exists
+		if _, err := os.Stat(args[0]); os.IsNotExist(err) {
+			os.Stderr.WriteString("source: file does not exist\n")
+			return
+		}
+
+		sourceFile(args[0])
+	default:
+		//Check if command is a file
+		cmd, err := findCommand(cmd)
+		if err != nil {
+			os.Stderr.WriteString(err.Error() + "\n")
+			return
+		}
+
+		// If last argument is &, execute command in background
+		if len(args) > 0 && args[len(args)-1] == "&" {
+			// Execute command in background
+		} else {
+			out, err := exec.Command(cmd, args...).Output()
+			if err != nil {
+				os.Stderr.WriteString(err.Error() + "\n")
+			}
+			fmt.Printf("%s", out)
+		}
+	}
+}
+
+func findCommand(cmd string) (string, error) {
+	if _, err := os.Stat(cmd); err == nil {
+		// Execute file
+		return cmd, nil
+	} else {
+		// Search for command in PATH
+		path := os.Getenv("PATH")
+		for _, dir := range strings.Split(path, ":") {
+			// Check if command is in directory
+			// If it is, execute it
+			if _, err := os.Stat(dir + "/" + cmd); err == nil {
+				return dir + "/" + cmd, nil
+			}
+		}
+		return "", fmt.Errorf("command not found")
+	}
+}
+
+func replaceEnvVars(str string) string {
+
+	// If string is single quote, return string
+	if len(str) > 1 && str[0] == '\'' && str[len(str)-1] == '\'' {
+		return str
+	}
+
+	// Replace with $HOME if last character is ~
+	if len(str) > 0 && str[len(str)-1] == '~' {
+		userhome, err := os.UserHomeDir()
+		if err == nil {
+			str = strings.Replace(str, "~", userhome, -1)
+		}
+	}
+
+	// Replace ~ with $HOME if ~ is not followed by a character
+	if len(str) > 1 && str[0] == '~' && (str[1] < 'a' || str[1] > 'z') && (str[1] < 'A' || str[1] > 'Z') {
+		userhome, err := os.UserHomeDir()
+		if err == nil {
+			str = strings.Replace(str, "~", userhome, 1)
+		}
+	}
+
+	// Replace ~user with home directory of user
+	if len(str) > 2 && str[0] == '~' && (str[1] >= 'a' && str[1] <= 'z' || str[1] >= 'A' && str[1] <= 'Z') {
+		var username string
+		for i := 1; i < len(str); i++ {
+			if str[i] == '/' {
+				break
+			} else {
+				username += string(str[i])
+			}
+		}
+		usr, err := user.Lookup(username)
+		if err == nil {
+			str = strings.Replace(str, "~"+username, usr.HomeDir, 1)
+		}
+	}
+
+	// Replace $VAR with value of VAR
+	// (first char is $, second char is [a-zA-Z_] and rest are [a-zA-Z0-9_])
+	for i := 0; i < len(str); i++ {
+		if str[i] == '$' && str[i+1] != '{' {
+			var varName string
+			for j := i + 1; j < len(str); j++ {
+				if (str[j] < 'a' || str[j] > 'z') && (str[j] < 'A' || str[j] > 'Z') && (str[j] < '0' || str[j] > '9') && str[j] != '_' {
+					break
+				} else {
+					varName += string(str[j])
+				}
+			}
+			varValue := os.Getenv(varName)
+			str = strings.Replace(str, "$"+varName, varValue, 1)
+		}
+	}
+
+	// Replace ${VAR} with value of VAR
+	// (first char is $, second char is {, third char is [a-zA-Z_] and rest are [a-zA-Z0-9_], last char is })
+	for i := 0; i < len(str); i++ {
+		if str[i] == '$' && str[i+1] == '{' {
+			var varName string
+			for j := i + 2; j < len(str); j++ {
+				if str[j] == '}' {
+					break
+				} else {
+					varName += string(str[j])
+				}
+			}
+			varValue := os.Getenv(varName)
+			str = strings.Replace(str, "${"+varName+"}", varValue, 1)
+		}
+	}
+
+	return str
+}
+
+func stringToCommandArgs(str string) (string, []string) {
+	var cmd string
+	var args []string
+	var inSingleQuotes bool
+	var inDoubleQuotes bool
+	var currentArg string
+
+	for _, char := range str {
+		if char == '"' && !inSingleQuotes {
+			inDoubleQuotes = !inDoubleQuotes
+		} else if char == '\'' && !inDoubleQuotes {
+			inSingleQuotes = !inSingleQuotes
+		} else if char == ' ' && !inSingleQuotes && !inDoubleQuotes {
+			if cmd == "" {
+				cmd = currentArg
+			} else {
+				args = append(args, currentArg)
+			}
+			currentArg = ""
+		} else {
+			currentArg += string(char)
+		}
+	}
+
+	if cmd == "" {
+		cmd = currentArg
+	} else {
+		args = append(args, currentArg)
+	}
+
+	for i, arg := range args {
+		arg = replaceEnvVars(arg)
+		args[i] = arg
+	}
+	return cmd, args
+}
+
+func sourceFile(path string) {
+	// Panic if file does not exist
+	if _, err := os.Stat(path); os.IsNotExist(err) {
+		panic(err)
+	}
+
+	file, err := os.Open(OtterRC)
+	if err != nil {
+		panic(err)
+	}
+
+	scanner := bufio.NewScanner(file)
+	for scanner.Scan() {
+		cmd, args := stringToCommandArgs(scanner.Text())
+		executeCommand(cmd, args)
+	}
+	file.Close()
+}
+
+func main() {
+	// Get user home directory
+	userhome, err := os.UserHomeDir()
+	if err != nil {
+		panic(err)
+	}
+	otterHistory := userhome + OtterHistory
+	otterRC := userhome + OtterRC
+
+	term, err := terminal.NewWithStdInOut()
+	if err != nil {
+		panic(err)
+	}
+
+	// If .otterhistory file does not exist, create it else read it
+	if _, err := os.Stat(otterHistory); os.IsNotExist(err) {
+		file, err := os.Create(otterHistory)
+		if err != nil {
+			panic(err)
+		}
+		file.Close()
+	} else {
+		file, err := os.Open(otterHistory)
+		if err != nil {
+			panic(err)
+		}
+		scanner := bufio.NewScanner(file)
+		for scanner.Scan() {
+			term.AddToHistory(scanner.Text())
+		}
+		file.Close()
+	}
+
+	// Welcome message
+	fmt.Println("Welcome to Otter 🦦 Shell!")
+	term.SetPrompt(Prompt)
+
+	// If .otterrc file does not exist, create it else read it
+	if _, err := os.Stat(otterRC); os.IsNotExist(err) {
+		file, err := os.Create(otterRC)
+		if err != nil {
+			panic(err)
+		}
+		file.Close()
+	} else {
+		sourceFile(otterRC)
+	}
+
+	line, err := term.ReadLine()
+
+	for {
+		// If command is EOF (but not empty string), exit
+		if err == io.EOF {
+			term.Write([]byte(line))
+			fmt.Println()
+			return
+		}
+		if !((err != nil && strings.Contains(err.Error(), "control-c break")) || len(line) == 0) {
+			// Add command to .otterhistory file
+			file, err := os.OpenFile(otterHistory, os.O_APPEND|os.O_WRONLY, 0644)
+			if err != nil {
+				panic(err)
+			}
+			file.WriteString(line + "\n")
+			file.Close()
+
+			// Parse command
+			cmd, args := stringToCommandArgs(line)
+			executeCommand(cmd, args)
+		}
+		line, err = term.ReadLine()
+	}
+}
diff --git a/src/maths/main.go b/src/maths/main.go
new file mode 100644
index 0000000..1c5a397
--- /dev/null
+++ b/src/maths/main.go
@@ -0,0 +1,15 @@
+package maths
+
+func Max(i, j int) int {
+	if i > j {
+		return i
+	}
+	return j
+}
+
+func Min(i, j int) int {
+	if i < j {
+		return i
+	}
+	return j
+}
diff --git a/src/terminal/terminal.go b/src/terminal/terminal.go
index b99d5a0..787fbc7 100644
--- a/src/terminal/terminal.go
+++ b/src/terminal/terminal.go
@@ -1,7 +1,3 @@
-// Copyright 2011 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
 package terminal
 
 import (
@@ -9,27 +5,15 @@ import (
 	"io"
 	"os"
 	"sync"
+
+	"github.com/k3y0708/otter/maths"
 )
 
-func max(i, j int) int {
-	if i > j {
-		return i
-	}
-	return j
-}
-
-func min(i, j int) int {
-	if i < j {
-		return i
-	}
-	return j
-}
-
 // historyIdxValue returns an index into a valid range of history
 func historyIdxValue(idx int, history [][]byte) int {
 	out := idx
-	out = min(len(history), out)
-	out = max(0, out)
+	out = maths.Min(len(history), out)
+	out = maths.Max(0, out)
 	return out
 }
 
@@ -457,7 +441,7 @@ func (t *Terminal) handleKey(key int) (line string, ok bool) {
 		if t.echo {
 			t.writeLine(t.line[t.pos-1:])
 		}
-		t.pos ++
+		t.pos++
 		t.moveCursorToPos(t.pos)
 		t.queue([]byte("\r\n"))
 		t.line = make([]byte, 0, 0)
@@ -603,6 +587,13 @@ func (t *Terminal) ReadLine() (line string, err error) {
 	return t.readLine()
 }
 
+func (t *Terminal) AddToHistory(line string) {
+	b := []byte(line)
+	h := make([]byte, len(b))
+	copy(h, b)
+	t.history = append(t.history, h)
+}
+
 func (t *Terminal) readLine() (line string, err error) {
 	// t.lock must be held at this point
 
@@ -642,10 +633,7 @@ func (t *Terminal) readLine() (line string, err error) {
 		if lineOk {
 			if t.echo { //&& len(line) > 0 {
 				// don't put passwords into history...
-				b := []byte(line)
-				h := make([]byte, len(b))
-				copy(h, b)
-				t.history = append(t.history, h)
+				t.AddToHistory(line)
 			}
 			return
 		}
@@ -683,22 +671,6 @@ func (t *Terminal) SetSize(width, height int) {
 	t.termWidth, t.termHeight = width, height
 }
 
-func (t *Terminal) SetHistory(h []string) {
-	// t.history = make([][]byte, len(h))
-	// for i := range h {
-	// 	t.history[i] = []byte(h[i])
-	// }
-	// //	t.historyIdx = len(h)
-}
-
-func (t *Terminal) GetHistory() (h []string) {
-	// h = make([]string, len(t.history))
-	// for i := range t.history {
-	// 	h[i] = string(t.history[i])
-	// }
-	return
-}
-
 type shell struct {
 	r io.Reader
 	w io.Writer