diff --git a/index.html b/index.html
index 5c80c99..488280d 100644
--- a/index.html
+++ b/index.html
@@ -20,7 +20,6 @@
       </div>
       <div>
         Data: {{ processor.mapData() }}
-
       </div>
 
       <div>
@@ -36,7 +35,7 @@
       </div>
 
       <div>
-        <input type="button" value="Download ROM">
+        <a id="mapLink" download="output.map" v-bind:href="mapData" type="application/octet-stream" v-on:click="downloadMapFile">Download MAP File</a>
       </div>
     </div>
 
diff --git a/script/app.js b/script/app.js
index 732d18d..d628593 100644
--- a/script/app.js
+++ b/script/app.js
@@ -2,20 +2,19 @@ let app = new Vue({
   el: '#app',
   data: {
     roms: [],
-    processor: new Processor([])
+    processor: new Processor([]),
+    mapData: ''
   },
   methods: {
     addFile: async function(e) {
-      this.roms.push(
-        new ROM(
-          await e.target.files[0].arrayBuffer()
-        )
-      );
-
-      console.log(this.roms)
+      this.roms.push(new ROM(await e.target.files[0].arrayBuffer()));
       this.processor.roms = this.roms;
 
       e.target.value = '';
+    },
+    downloadMapFile: function(e) {
+      if (this.mapData) { URL.revokeObjectURL(this.mapData) }
+      this.mapData = URL.createObjectURL(new Blob([this.processor.mapData()]));
     }
   }
 });
diff --git a/script/gbnp.js b/script/gbnp.js
index 4b59f86..aa607d4 100644
--- a/script/gbnp.js
+++ b/script/gbnp.js
@@ -5,9 +5,8 @@ const CARTRIDGE_TYPES = [
   'ROM+RAM', 'ROM+RAM+BATTERY', null, null, null, null, null,
   'MBC3+TIMER+BATTERY', 'MBC3+TIMER+RAM+BATTERY', 'MBC3', 'MBC3+RAM', 'MBC3+RAM+BATTERY', null, null, null, null, null,
   'MBC5', 'MBC5+RAM', 'MBC5+RAM+BATTERY', 'MBC5+RUMBLE', 'MBC5+RUMBLE+RAM', 'MBC5+RUMBLE+RAM+BATTERY'
-]
-
-const FINAL_BYTES = [0x02, 0x00, 0x30, 0x12, 0x99, 0x11, 0x12, 0x20, 0x37, 0x57, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0x00, 0x00]
+];
+const MAP_TRAILER_BYTES = [0x02, 0x00, 0x30, 0x12, 0x99, 0x11, 0x12, 0x20, 0x37, 0x57, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0x00, 0x00];
 
 class ROM {
   constructor(arrayBuffer) {
@@ -68,10 +67,10 @@ class Processor {
 
   mapData() {
     const mapBuffer = new ArrayBuffer(128);
-    let map = new FileSeeker(mapBuffer);
+    const mapFile = new FileSeeker(mapBuffer);
 
     // write mbc type, rom size, and ram size for menu
-    map.writeBytes([0xA8, 0, 0]);
+    mapFile.writeBytes([0xA8, 0, 0]);
 
     // write mbc type, rom size, and ram size for each rom
     let romOffset = 128;
@@ -82,14 +81,14 @@ class Processor {
       let bits = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0] // 16
 
       // set mbc bits
-      let tb = rom.type_byte
-      if (tb >= 0x01 || tb <= 0x30) {
+      let tb = rom.typeByte
+      if (tb >= 0x01 && tb <= 0x03) {
         bits[15] = 0; bits[14] = 0; bits[13] = 1;
-      } else if (tb >= 0x05 || tb <= 0x06) {
+      } else if (tb >= 0x05 && tb <= 0x06) {
         bits[15] = 0; bits[14] = 1; bits[13] = 0;
-      } else if (tb >= 0xF || tb <= 0x13 ) {
+      } else if (tb >= 0x0F && tb <= 0x13 ) {
         bits[15] = 0; bits[14] = 1; bits[13] = 1;
-      } else if (tb >= 0x19 || tb <= 0x1E ) {
+      } else if (tb >= 0x19 && tb <= 0x1E ) {
         bits[15] = 1; bits[14] = 0; bits[13] = 0;
       }
 
@@ -122,23 +121,27 @@ class Processor {
 
       // rom offset and cart info bits
       bits.reverse();
-      let bytes = [parseInt(bits.slice(0, 8), 2), parseInt(bits.slice(8, 16), 2)]
+      let bytes = [parseInt(bits.slice(0, 8).join(''), 2), parseInt(bits.slice(8, 16).join(''), 2)]
       bytes[1] = bytes[1] | Math.trunc(romOffset / 32);
-      console.log(bytes)
-      map.writeBytes(bytes)
+      mapFile.writeBytes(bytes)
       romOffset += rom.paddedRomSizeKB();
 
       // ram offset
-      map.writeByte(Math.trunc(ramOffset / 2));
+      mapFile.writeByte(Math.trunc(ramOffset / 2));
       ramOffset += (rom.typeByte == 0x06 || rom.ramSizeKB() < 8) ? 8 : rom.ramSizeKB();
     }
 
     // trailer
-    map.writeByteUntil(0xFF, 127 - FINAL_BYTES.length);
-    map.writeBytes(FINAL_BYTES);
+    mapFile.writeByteUntil(0xFF, 128 - FINAL_BYTES.length);
+    mapFile.writeBytes(FINAL_BYTES);
 
     return new Uint8Array(mapBuffer);
   }
+
+  romData() {
+    const romBuffer = new ArrayBuffer(math.pow(1024, 2));
+    const romFile = new FileSeeker(romBuffer);
+  }
 }
 
 class FileSeeker {
@@ -170,14 +173,13 @@ class FileSeeker {
   }
 
   writeByte(byte) {
-    console.log(byte)
     this.view.setUint8(this.position, byte);
     this.position++;
   }
 
   writeBytes(bytes) {
-    for (const byte in bytes) {
-      this.writeByte(byte);
+    for (let i = 0; i < bytes.length; i++) {
+      this.writeByte(bytes[i]);
     }
   }