diff --git a/.gitignore b/.gitignore
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+++ b/.gitignore
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+test/
+dist/
+build/
+.venv/
+*.zip
+main.spec
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diff --git a/assets/favicon.ico b/assets/favicon.ico
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diff --git a/main.py b/main.py
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+++ b/main.py
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+import customtkinter as ctk
+from tkinter import filedialog, messagebox
+
+ctk.set_appearance_mode("System")
+ctk.set_default_color_theme("dark-blue")
+
+class MainApp(ctk.CTk):
+    def __init__(self):
+        super().__init__()
+
+        self.title("Liskod")
+        self.geometry("400x403")
+        self.resizable(False, False)
+
+        # --- Data State ---
+        self.current_file_path = None
+        self.list_in_memory = []
+        self.set_in_memory = set()
+        self.any_change = False
+
+        # --- Grid Configuration ---
+        self.grid_rowconfigure(0, weight=0)
+        self.grid_rowconfigure(1, weight=0)
+        self.grid_rowconfigure(2, weight=0)
+        self.grid_columnconfigure(0, weight=1)
+
+        # ============================================================
+        # ROW 0: File Input & Mode Checkbox
+        # ============================================================
+        self.row1_frame = ctk.CTkFrame(self)
+        self.row1_frame.grid(row=0, column=0, padx=20, pady=(15, 10), sticky="ew")
+        self.row1_frame.grid_columnconfigure(0, weight=1)
+        self.row1_frame.grid_columnconfigure(1, weight=0)
+
+        self.var_edit_mode = ctk.BooleanVar(value=False)
+        self.chk_mode = ctk.CTkCheckBox(
+            self.row1_frame, 
+            text="Edit Existing File", 
+            font=("Arial", 14),
+            variable=self.var_edit_mode,
+            command=self.toggle_confirm
+        )
+        self.chk_mode.grid(row=0, column=0, padx=10, pady=(15, 5), sticky="w")
+
+        self.sort_toggle = ctk.BooleanVar(value=False)
+        self.chk_mode2 = ctk.CTkCheckBox(
+            self.row1_frame, 
+            text="Sort Out", 
+            font=("Arial", 14),
+            variable=self.sort_toggle,
+            command=None
+        )
+        self.chk_mode2.grid(row=0, column=1, pady=(15, 5), sticky="e")
+
+        self.entry_filepath = ctk.CTkEntry(
+            self.row1_frame, 
+            text_color="gray",
+            font=("Arial", 14),
+            placeholder_text="New File (Save As)",
+            height=35
+            )
+        self.entry_filepath.grid(row=1, column=0, padx=(10, 0), pady=5, sticky="ew")
+        self.entry_filepath.configure(state="disabled")
+
+        self.btn_browse = ctk.CTkButton(
+            self.row1_frame, 
+            text="Browse", 
+            command=self.browse_file, 
+            width=80, 
+            height=35,
+            font=("Arial", 14),
+            )
+        self.btn_browse.grid(row=1, column=1, padx=(10, 10), pady=10)
+
+        # ============================================================
+        # ROW 1: Preview Window
+        # ============================================================
+        self.preview_frame = ctk.CTkFrame(self)
+        self.preview_frame.grid(row=1, column=0, padx=20, pady=(5, 10), sticky="ew")
+        self.preview_frame.grid_columnconfigure(0, weight=1)
+
+        self.lbl_preview = ctk.CTkLabel(self.preview_frame, text="Preview", font=("Arial", 14))
+        self.lbl_preview.grid(row=0, column=0, padx=10, pady=(5, 0), sticky="w")
+
+        self.txt_preview = ctk.CTkTextbox(self.preview_frame, height=110) 
+        self.txt_preview.grid(row=1, column=0, padx=10, pady=(5, 10), sticky="ew")
+        self.txt_preview.configure(state="disabled") 
+
+        self.input_container = ctk.CTkFrame(self.preview_frame, fg_color="transparent")
+        self.input_container.grid(row=2, column=0, padx=10, pady=(5, 10), sticky="ew")
+        self.input_container.grid_columnconfigure(0, weight=1)
+
+        self.entry_text = ctk.CTkEntry(self.input_container, placeholder_text="Type content here...", height=35, font=("Arial", 14))
+        self.entry_text.grid(row=0, column=0, padx=(0, 10), sticky="ew")
+        self.entry_text.bind("<Return>", lambda event: self.add_line_to_memory())
+
+        self.btn_add = ctk.CTkButton(
+            self.input_container, 
+            text="Add", 
+            width=80, 
+            font=("Arial", 14),
+            command=self.add_line_to_memory, 
+            height=35
+            )
+        self.btn_add.grid(row=0, column=1, sticky="e")
+
+        # ============================================================
+        # ROW 2: Save Button
+        # ============================================================
+        self.row3_frame = ctk.CTkFrame(self, fg_color="transparent")
+        self.row3_frame.grid(row=3, column=0, padx=20, pady=(5, 20), sticky="ew")
+        self.row3_frame.grid_columnconfigure(0, weight=0)
+        self.row3_frame.grid_columnconfigure(1, weight=0)
+
+        self.last_status = ctk.CTkLabel(
+            self.row3_frame, 
+            height=35, 
+            width=290, 
+            fg_color="#282828",
+            corner_radius=4,
+            text_color="gray",
+            text="Status",
+            font=("Arial", 14),
+            ) 
+        self.last_status.grid(row=0, column=0, padx=(0, 10), sticky="ew")
+
+        self.btn_save = ctk.CTkButton(
+            self.row3_frame,
+            text="Save",
+            height=35,
+            width=60,
+            font=("Arial", 14),
+            fg_color="green",
+            hover_color="darkgreen",
+            command=self.save_action
+        )
+        self.btn_save.grid(row=0, column=1, sticky="e")
+        self.toggle_mode()
+
+        self.protocol("WM_DELETE_WINDOW", self.on_closing)
+
+    # --- Logic Methods ---
+
+    def toggle_confirm(self):
+        if len(self.list_in_memory) > 0:
+            new_state = self.var_edit_mode.get()
+            action = "enable" if new_state else "disable"
+
+            answer = messagebox.askyesno(
+                title="Confirmation",
+                message=f"Are you sure you want to {action} this setting?"
+            )
+            if answer:
+                self.delete_memory()
+                self.update_preview()
+                self.toggle_mode()
+            else:
+                self.var_edit_mode.set(not new_state)
+        else:
+            self.toggle_mode()
+            self.update_preview()
+
+
+    def toggle_mode(self):
+        new_state = self.var_edit_mode.get()
+
+        if new_state:
+            # Checked: Edit Existing Mode
+            self.btn_browse.configure(state="normal")
+            self.entry_filepath.configure(state="normal")
+            self.entry_filepath.delete(0, "end")
+            if self.current_file_path:
+                self.entry_filepath.insert(0, f"...{self.current_file_path[-30:]}")
+            else:
+                self.entry_filepath.insert(0, "No file loaded...")
+                self.btn_add.configure(state="disabled")
+            self.entry_filepath.configure(state="disabled")
+        else:
+            # Unchecked: New File Mode
+            self.current_file_path = None
+            self.btn_browse.configure(state="disabled")
+            self.btn_add.configure(state="normal")
+            self.entry_filepath.configure(state="normal")
+            self.entry_filepath.delete(0, "end")
+            self.entry_filepath.insert(0, "Create New File")
+            self.entry_filepath.configure(state="disabled")
+
+
+    def browse_file(self):
+        filename = filedialog.askopenfilename(
+            title="Select a Text File",
+            filetypes=[("Text files", "*.txt")]
+        )
+
+        if filename:
+            if not filename.lower().endswith('.txt'):
+                messagebox.showerror("Error", "Only .txt files are allowed!")
+                return
+
+            self.current_file_path = filename
+            
+            self.entry_filepath.configure(state="normal")
+            self.entry_filepath.delete(0, "end")
+            self.entry_filepath.insert(0, f"...{filename[-30:]}")
+            self.entry_filepath.configure(state="disabled")
+
+            try:
+                with open(filename, "r", encoding="utf-8") as f:
+                    self.list_in_memory = [line.strip() for line in f]
+
+                self.set_in_memory = set(self.list_in_memory)
+                duplicates = len(self.list_in_memory) - len(self.set_in_memory)
+                self.last_status.configure(
+                    text=f"File loaded, {duplicates} duplicate(s) removed",
+                    text_color="#9efc90"
+                    )
+                self.list_in_memory = list(dict.fromkeys(self.list_in_memory))
+
+                self.btn_add.configure(state="normal")
+                self.update_preview()
+
+            except Exception as e:
+                messagebox.showerror("Error", f"Could not read file:\n{e}")
+                self.last_status.configure(
+                    text=f"Could not read file:\n{e}",
+                    text_color="#ff9d9d"
+                    )
+
+
+    def add_line_to_memory(self):
+        text = self.entry_text.get()
+        if not text:
+            return 
+
+        clean_text = text.replace('\n', '').replace('\r', '').strip()
+        if clean_text in self.set_in_memory:
+            self.entry_text.delete(0, "end")
+            self.last_status.configure(
+                text=f"Line \"{clean_text[:10]}\" already exists!",
+                text_color="#ff9d9d"
+                )
+        else:
+            if not len(clean_text) == 0:
+                self.any_change = True
+                self.list_in_memory.append(clean_text)
+                self.set_in_memory.add(clean_text)
+                self.entry_text.delete(0, "end")
+                self.update_preview()
+                self.last_status.configure(
+                    text=f"Line \"{clean_text[:10]}\" added!",
+                    text_color="#9efc90"
+                    )
+            self.entry_text.delete(0, "end")
+
+
+    def delete_memory(self):
+        self.list_in_memory = []
+        self.set_in_memory = set()
+
+
+    def update_preview(self):
+        self.txt_preview.configure(state="normal")
+        self.txt_preview.delete("1.0", "end")
+
+        if not self.list_in_memory:
+            display_text = ""
+        elif len(self.list_in_memory) > 5:
+            last_five = ["..."] + self.list_in_memory[-5:]
+            display_text = "\n".join(last_five)
+        else:
+            last_five = self.list_in_memory[-5:]
+            display_text = "\n".join(last_five)
+
+        self.txt_preview.insert("1.0", display_text)
+        self.txt_preview.configure(state="disabled")
+
+
+    def save_action(self):
+        if len(self.list_in_memory) <= 0:
+            return
+
+        target_path = filedialog.asksaveasfilename(
+            title="Save As",
+            defaultextension=".txt",
+            filetypes=[("Text files", "*.txt")]
+        )
+        if not target_path:
+            return
+
+        try:
+            with open(target_path, "w", encoding="utf-8") as f:
+                to_be_saved = self.list_in_memory
+                if self.sort_toggle.get():
+                    to_be_saved = sorted(self.list_in_memory)
+                full_content = "\n".join(to_be_saved)
+                f.write(full_content)
+            
+            self.any_change = False
+            self.last_status.configure(
+                text="File saved successfully!",
+                text_color="#9efc90"
+                )
+            self.var_edit_mode.set(True)
+            self.current_file_path = target_path
+
+            self.entry_filepath.configure(state="normal")
+            self.entry_filepath.delete(0, "end")
+            self.entry_filepath.insert(0, f"...{self.current_file_path[-30:]}")
+            self.entry_filepath.configure(state="disabled")
+            
+        except Exception as e:
+            self.last_status.configure(
+                text=f"Could not save file:\n{e}",
+                text_color="#ff9d9d"
+                )
+            
+    def on_closing(self):
+        if self.any_change:
+            if messagebox.askokcancel("Quit", "There are unsaved changes, are you sure you want to quit?"):
+                self.destroy()
+            return
+        else:
+            self.destroy()
+
+if __name__ == "__main__":
+    app = MainApp()
+    app.mainloop()
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