diff --git a/assembler_6502.rb b/assembler_6502.rb
index 8cfbcc2..2929aed 100755
--- a/assembler_6502.rb
+++ b/assembler_6502.rb
@@ -93,10 +93,20 @@ module Assembler6502
       STDERR.puts "Missing options try --help"
       exit(1)
     end
-    Assembler6502::Assembler.from_file(input_file, options[:out_file])
+
+    begin
+      Assembler6502::Assembler.from_file(input_file, options[:out_file])
+    rescue StandardError => error
+      STDERR.puts("Assemble Failed!")
+      STDERR.puts(error.class)
+      if error.message
+        STDERR.puts(error.message)
+      end
+      exit(1)
+    end
   end
   module_function :run
 
 end
 
-Assembler6502.run
+  Assembler6502.run
diff --git a/lib/assembler.rb b/lib/assembler.rb
index f069283..2d2f2f1 100644
--- a/lib/assembler.rb
+++ b/lib/assembler.rb
@@ -47,6 +47,7 @@ module Assembler6502
 
     ##  Custom exceptions
     class INESHeaderNotFound < StandardError; end
+    class MapperNotSupported < StandardError; end
 
 
     ####
@@ -152,48 +153,6 @@ module Assembler6502
     end
 
 
-    ####
-    ##  After assembling the binary into the full 16-bit memory space
-    ##  we can now slice out the parts that should go into the binary ROM
-    ##  I am guessing the ROM size should be 1 bank of 16KB cartridge ROM
-    ##  plus the 16 byte iNES header.  If the ROM is written into memory 
-    ##  beginning at 0xC000, this should reach right up to the interrupt vectors
-    def assemble_old
-      virtual_memory = assemble_in_virtual_memory
-
-      ##  First we need to be sure we have an iNES header
-      fail(INESHeaderNotFound) if @ines_header.nil?
-
-      ##  Create memory to hold the ROM
-      nes_rom = MemorySpace.new(0x10 + 0x4000)
-
-      ##  First write the iNES header itself
-      nes_rom.write(0x0, @ines_header.emit_bytes)
-
-      ##  Write only one PROG section from 0xC000
-      start_address = 0xC000
-      length = 0x4000
-      prog_rom = virtual_memory.read(start_address, length)
-      write_start = 0x10
-      nes_rom.write(write_start, prog_rom)
-
-      ##  Now try writing one CHR-ROM section from 0x0000
-      start_address = 0x0000
-      length = 0x4000
-      char_rom = virtual_memory.read(start_address, length)
-      write_start = 0x10 + 0x4000
-      nes_rom.write(write_start, char_rom)
-
-      nes_rom.emit_bytes
-
-      #rom_size = 16 + (0xffff - 0xc000)
-      #nes_rom = MemorySpace.new(rom_size)
-      #nes_rom.write(0x0, virtual_memory.read(0x0, 0x10))
-      #nes_rom.write(0x10, virtual_memory.read(0xC000, 0x4000))
-      #nes_rom.emit_bytes
-    end
-
-
     ####
     ##  New ROM assembly, this is so simplified, and needs to take banks into account
     ##  This will happen once I fully understand mappers and banks.
@@ -201,6 +160,9 @@ module Assembler6502
       ##  Assemble into a virtual memory space
       virtual_memory = assemble_in_virtual_memory
 
+      ##  First we need to be sure we have an iNES header
+      fail(MapperNotSupported, "Mapper #{@ines_header.mapper} not supported") if @ines_header.mapper != 0
+
       ##  First we need to be sure we have an iNES header
       fail(INESHeaderNotFound) if @ines_header.nil?
 
diff --git a/scroll.asm b/scroll.asm
index c0afde0..8986f36 100644
--- a/scroll.asm
+++ b/scroll.asm
@@ -20,6 +20,7 @@
   ;    *dx     = $00    ;  The speed delta x of the sprite
   ;    *a      = $01    ;  Whether the A button is down
   ;    *scroll = $02    ;  The scroll amount
+  ;    *dy     = $03    ;  The speed delta y of the sprite
   ;
   ;    *sprite = $200   ;  Some sprite memory
   ;  Actually I can probably do this with a .org and label pair
@@ -116,7 +117,7 @@ init_sprites:
   lda #$00
   ldx #$00
 sprite_clear1:
-  sta $0200, X             ; $0200 = sprite
+  sta sprite, x
   inx
   bne sprite_clear1
 
@@ -131,6 +132,9 @@ sprite_clear1:
   ; Set initial value of dx
   lda #$01
   sta $00                 ;  dx = $00
+  ; Set initial value of dy
+  lda #$70
+  sta $03                 ;  dy = $03
   rts
 
 ; Load palette into $3F00