diff --git a/experimental/src/main.rs b/experimental/src/main.rs
index b473100..2387026 100644
--- a/experimental/src/main.rs
+++ b/experimental/src/main.rs
@@ -1,9 +1,9 @@
 #![cfg_attr(not(debug_assertions), windows_subsystem = "windows")] // hide console window on Windows in release
 
-use std::path::PathBuf;
+use std::fs;
 
-use eframe::{egui::{self, text::{LayoutJob, TextWrapping}, ColorImage, Image, Rgba, TextBuffer, TextureFilter, TextureHandle, TextureOptions}, epaint::Fonts};
-use luca_pak::{entry::EntryType, header, Pak};
+use eframe::egui::{self, ColorImage, Image, TextureFilter, TextureHandle, TextureOptions};
+use luca_pak::{entry::EntryType, Pak};
 
 fn main() -> eframe::Result {
     let options = eframe::NativeOptions {
@@ -47,15 +47,27 @@ impl eframe::App for PakExplorer {
             ctx.set_pixels_per_point(1.5);
             ui.heading("PAK File Explorer");
 
-            if ui.button("Open file…").clicked() {
-                if let Some(path) = rfd::FileDialog::new().pick_file() {
-                    let pak = Pak::open(&path).unwrap();
-                    self.open_file = Some(pak);
-                    self.selected_entry = None;
-                    self.image_texture = None;
-                    self.hex_string = None;
+            ui.horizontal(|ui| {
+                if ui.button("Open file…").clicked() {
+                    if let Some(path) = rfd::FileDialog::new().pick_file() {
+                        let pak = Pak::open(&path).unwrap();
+                        self.open_file = Some(pak);
+                        self.selected_entry = None;
+                        self.image_texture = None;
+                        self.hex_string = None;
+                    }
                 }
-            }
+                if let Some(pak) = &self.open_file {
+                    if ui.button("Save PAK…").clicked() {
+                        if let Some(path) = rfd::FileDialog::new()
+                                .set_file_name(pak.path().file_name().unwrap().to_string_lossy())
+                                .save_file()
+                        {
+                            pak.save(&path).unwrap();
+                        }
+                    }
+                }
+            });
 
             ui.separator();
 
@@ -92,14 +104,25 @@ impl eframe::App for PakExplorer {
             }
 
             if let Some(entry) = &self.selected_entry {
-                if ui.button("Save entry…").clicked() {
-                    if let Some(path) = rfd::FileDialog::new()
-                        .set_file_name(entry.display_name())
-                        .save_file()
-                    {
-                        entry.save(&path).unwrap();
+                ui.horizontal(|ui| {
+                    if ui.button("Save entry…").clicked() {
+                        if let Some(path) = rfd::FileDialog::new()
+                            .set_file_name(entry.display_name())
+                            .save_file()
+                        {
+                            entry.save(&path).unwrap();
+                        }
                     }
-                }
+
+                    if let Some(pak) = &mut self.open_file.as_mut() {
+                        if ui.button("Replace entry…").clicked() {
+                            if let Some(path) = rfd::FileDialog::new().pick_file() {
+                                let file_bytes = fs::read(path).unwrap();
+                                pak.replace(entry.index(), &file_bytes).unwrap();
+                            }
+                        }
+                    }
+                });
                 match entry.file_type() {
                     EntryType::CZ0 | EntryType::CZ1
                         | EntryType::CZ2 | EntryType::CZ3
@@ -147,7 +170,7 @@ impl eframe::App for PakExplorer {
                         );
                     },
                 }
-            } else {
+            } else if self.open_file.is_some() {
                 ui.centered_and_justified(|ui|
                     ui.label("Select an Entry")
                 );
diff --git a/luca_pak/src/entry.rs b/luca_pak/src/entry.rs
index bb7d443..16b3273 100644
--- a/luca_pak/src/entry.rs
+++ b/luca_pak/src/entry.rs
@@ -1,5 +1,5 @@
 use std::{
-    error::Error, fmt, fs::File, io::{BufWriter, Write}, path::Path
+    error::Error, fs::File, io::{BufWriter, Write}, path::Path
 };
 
 /// A single file entry in a PAK file
diff --git a/luca_pak/src/lib.rs b/luca_pak/src/lib.rs
index 5e91ffa..0ae15d0 100644
--- a/luca_pak/src/lib.rs
+++ b/luca_pak/src/lib.rs
@@ -213,7 +213,6 @@ impl Pak {
         &self,
         mut output: &mut T
     ) -> Result<(), PakError> {
-        let mut block_offset = 0;
         self.header.write_into(&mut output)?;
 
         // Write unknown data
@@ -254,21 +253,22 @@ impl Pak {
 
         output.write_all(&self.unknown_post_header)?;
 
-        block_offset += self.header().data_offset / self.header().block_size;
+        //let mut block_offset = self.header().data_offset / self.header().block_size;
 
         for entry in self.entries() {
-            let block_size = entry.data.len().div_ceil(self.header().block_size as usize);
+            //let block_size = entry.data.len().div_ceil(self.header().block_size as usize);
             let mut remainder = 2048 - entry.data.len().rem_euclid(self.header().block_size as usize);
             if remainder == 2048 {
                 remainder = 0;
             }
+            output.write_all(&entry.data)?;
+            output.write_all(&vec![0u8; remainder])?;
 
             //println!("entry len {}", entry.data.len());
             //println!("remainder {}", remainder);
             //println!("block_offset {} - expected offset {}", block_offset, entry.offset);
-            output.write_all(&entry.data)?;
-            output.write_all(&vec![0u8; remainder])?;
-            block_offset += block_size as u32;
+
+            //block_offset += block_size as u32;
         }
 
         Ok(())