diff --git a/app/build.gradle b/app/build.gradle
index 94048ba..0a6df84 100644
--- a/app/build.gradle
+++ b/app/build.gradle
@@ -26,9 +26,8 @@ dependencies {
   implementation 'com.google.android.material:material:1.0.0-alpha1'
   implementation 'androidx.appcompat:appcompat:1.0.0-alpha1'
   implementation 'androidx.cardview:cardview:1.0.0-alpha1'
-  implementation 'org.jetbrains.kotlin:kotlin-stdlib:1.2.60'
-  implementation "org.jetbrains.kotlin:kotlin-reflect:1.2.60"
-  implementation 'com.facebook.stetho:stetho:1.5.0'
+  implementation 'org.jetbrains.kotlin:kotlin-stdlib:1.2.61'
+  implementation "org.jetbrains.kotlin:kotlin-reflect:1.2.61"
 
   testImplementation 'junit:junit:4.12'
   testImplementation 'com.google.truth:truth:0.42'
diff --git a/app/src/main/kotlin/android/emu6502/Emu6502Application.kt b/app/src/main/kotlin/android/emu6502/Emu6502Application.kt
index 8671e13..f0a7721 100644
--- a/app/src/main/kotlin/android/emu6502/Emu6502Application.kt
+++ b/app/src/main/kotlin/android/emu6502/Emu6502Application.kt
@@ -1,14 +1,7 @@
 package android.emu6502
 
 import android.app.Application
-import com.facebook.stetho.Stetho
 
 class Emu6502Application : Application() {
-  override fun onCreate() {
-    super.onCreate()
-    Stetho.initialize(Stetho.newInitializerBuilder(this)
-        .enableWebKitInspector(Stetho.defaultInspectorModulesProvider(this))
-        .build())
-  }
 }
 
diff --git a/app/src/main/kotlin/android/emu6502/nes/APU.kt b/app/src/main/kotlin/android/emu6502/nes/APU.kt
deleted file mode 100644
index c419b4e..0000000
--- a/app/src/main/kotlin/android/emu6502/nes/APU.kt
+++ /dev/null
@@ -1,5 +0,0 @@
-package android.emu6502.nes
-
-class APU {
-
-}
\ No newline at end of file
diff --git a/app/src/main/kotlin/android/emu6502/nes/Cartridge.kt b/app/src/main/kotlin/android/emu6502/nes/Cartridge.kt
deleted file mode 100644
index 95c9e90..0000000
--- a/app/src/main/kotlin/android/emu6502/nes/Cartridge.kt
+++ /dev/null
@@ -1,41 +0,0 @@
-package android.emu6502.nes
-
-import java.util.*
-
-data class Cartridge(
-    // @formatter:off
-    val pgr: IntArray,                        // PRG-ROM banks
-    val chr: IntArray,                        // CHR-ROM banks
-    val mapper: Byte,                         // mapper type
-    var mirror: Int,                          // mirroring mode
-    val battery: Byte,                        // battery present
-    val sram: IntArray = IntArray(0x2000)     // Save RAM
-    // @formatter:on
-) {
-
-  override fun equals(other: Any?): Boolean {
-    if (this === other) return true
-    if (other?.javaClass != javaClass) return false
-
-    other as Cartridge
-
-    if (!Arrays.equals(pgr, other.pgr)) return false
-    if (!Arrays.equals(chr, other.chr)) return false
-    if (!Arrays.equals(sram, other.sram)) return false
-    if (mapper != other.mapper) return false
-    if (mirror != other.mirror) return false
-    if (battery != other.battery) return false
-
-    return true
-  }
-
-  override fun hashCode(): Int {
-    var result = Arrays.hashCode(pgr)
-    result = 31 * result + Arrays.hashCode(chr)
-    result = 31 * result + Arrays.hashCode(sram)
-    result = 31 * result + mapper
-    result = 31 * result + mirror
-    result = 31 * result + battery
-    return result
-  }
-}
\ No newline at end of file
diff --git a/app/src/main/kotlin/android/emu6502/nes/Console.kt b/app/src/main/kotlin/android/emu6502/nes/Console.kt
deleted file mode 100644
index c0be513..0000000
--- a/app/src/main/kotlin/android/emu6502/nes/Console.kt
+++ /dev/null
@@ -1,33 +0,0 @@
-package android.emu6502.nes
-
-import android.emu6502.CPU
-import android.emu6502.Display
-import android.emu6502.Memory
-import android.emu6502.nes.mappers.Mapper
-
-class Console(
-    val cpu: CPU,
-    val apu: APU,
-    val ppu: PPU,
-    val cartridge: Cartridge,
-    val controller1: Controller,
-    val controller2: Controller,
-    val mapper: Mapper,
-    val ram: ByteArray = ByteArray(2048)
-) {
-  fun step() {
-
-  }
-
-  companion object {
-    fun newConsole(cartridge: Cartridge, display: Display): Console {
-      val ppu = PPU()
-      val memory = Memory(display)
-      val cpu = CPU(memory)
-      val mapper = Mapper.newMapper(cartridge, ppu, cpu)
-      val apu = APU()
-      return Console(cpu, apu, ppu, cartridge, Controller(), Controller(), mapper)
-    }
-  }
-}
-
diff --git a/app/src/main/kotlin/android/emu6502/nes/Controller.kt b/app/src/main/kotlin/android/emu6502/nes/Controller.kt
deleted file mode 100644
index 7d0dec9..0000000
--- a/app/src/main/kotlin/android/emu6502/nes/Controller.kt
+++ /dev/null
@@ -1,13 +0,0 @@
-package android.emu6502.nes
-
-class Controller {
-  var buttons: Array<Boolean> = Array(8) { false }
-  var index: Byte = 0
-  var strobe: Byte = 0
-
-  fun read() {
-  }
-
-  fun write() {
-  }
-}
\ No newline at end of file
diff --git a/app/src/main/kotlin/android/emu6502/nes/INESFileHeader.kt b/app/src/main/kotlin/android/emu6502/nes/INESFileHeader.kt
deleted file mode 100644
index 226ace2..0000000
--- a/app/src/main/kotlin/android/emu6502/nes/INESFileHeader.kt
+++ /dev/null
@@ -1,49 +0,0 @@
-package android.emu6502.nes
-
-import android.emu6502.nes.INESFileParser.Companion.INES_FILE_MAGIC
-import android.emu6502.nes.INESFileParser.Companion.PADDING
-import java.util.*
-
-// http://wiki.nesdev.com/w/index.php/INES
-// Sample header:
-// 4e  45  53  1a  10  10  40  00  00  00  00  00  00  00  00  00
-data class INESFileHeader(
-    val magic: ByteArray,   // Constant $4E $45 $53 $1A ("NES" followed by MS-DOS end-of-file)
-    val numPRG: Byte,       // Size of PRG ROM in 16 KB units
-    val numCHR: Byte,       // Size of CHR ROM in 8 KB units (Value 0 means the board uses CHR RAM)
-    val control1: Byte,     // Flags 6
-    val control2: Byte,     // Flags 7
-    val numRAM: Byte,       // Size of PRG RAM in 8 KB units
-    val padding: ByteArray // 7 bytes, unused
-) {
-  fun isValid() =
-      Arrays.equals(magic, INES_FILE_MAGIC) && Arrays.equals(padding, PADDING)
-
-  override fun equals(other: Any?): Boolean {
-    if (this === other) return true
-    if (other?.javaClass != javaClass) return false
-
-    other as INESFileHeader
-
-    if (!Arrays.equals(magic, other.magic)) return false
-    if (numPRG != other.numPRG) return false
-    if (numCHR != other.numCHR) return false
-    if (control1 != other.control1) return false
-    if (control2 != other.control2) return false
-    if (numRAM != other.numRAM) return false
-    if (!Arrays.equals(padding, other.padding)) return false
-
-    return true
-  }
-
-  override fun hashCode(): Int {
-    var result = Arrays.hashCode(magic)
-    result = 31 * result + numPRG
-    result = 31 * result + numCHR
-    result = 31 * result + control1
-    result = 31 * result + control2
-    result = 31 * result + numRAM
-    result = 31 * result + Arrays.hashCode(padding)
-    return result
-  }
-}
\ No newline at end of file
diff --git a/app/src/main/kotlin/android/emu6502/nes/INESFileParser.kt b/app/src/main/kotlin/android/emu6502/nes/INESFileParser.kt
deleted file mode 100644
index ef6f3d1..0000000
--- a/app/src/main/kotlin/android/emu6502/nes/INESFileParser.kt
+++ /dev/null
@@ -1,51 +0,0 @@
-package android.emu6502.nes
-
-import java.io.DataInputStream
-import java.io.File
-import java.io.InputStream
-
-internal class INESFileParser {
-  companion object {
-    internal val INES_FILE_MAGIC = byteArrayOf(0x4e, 0x45, 0x53, 0x1a)/*0x4e45531a*/
-    internal val PADDING = byteArrayOf(0, 0, 0, 0, 0, 0, 0)
-
-    internal fun parseFileHeader(stream: InputStream): INESFileHeader {
-      val dataStream = DataInputStream(stream.buffered())
-      return INESFileHeader(
-          (0..3).map { dataStream.readByte() }.toByteArray(),
-          dataStream.readByte(),
-          dataStream.readByte(),
-          dataStream.readByte(),
-          dataStream.readByte(),
-          dataStream.readByte(),
-          (0..6).map { dataStream.readByte() }.toByteArray())
-    }
-
-    internal fun parseCartridge(file: File): Cartridge =
-        file.inputStream().use {
-          val inesFileHeader = parseFileHeader(it)
-          // mapper type
-          val control1 = inesFileHeader.control1.toInt()
-          val mapper1 = control1 shr 4
-          val mapper2 = inesFileHeader.control2.toInt() shr 4
-          val mapper = mapper1 or (mapper2 shl 4)
-          // mirroring type
-          val mirror1 = control1 and 1
-          val mirror2 = (control1 shr 3) and 1
-          val mirror = mirror1 or (mirror2 shl 1)
-          // battery-backed RAM
-          val battery = (control1 shr 1).and(1).toByte()
-          // read prg-rom bank(s)
-          val prg = ByteArray(inesFileHeader.numPRG.toInt() * 16384)
-          it.read(prg)
-          // read chr-rom bank(s)
-          val chr = ByteArray(inesFileHeader.numCHR.toInt() * 8192)
-          it.read(chr)
-          return Cartridge(
-              prg.map(Byte::toInt).toIntArray(),
-              chr.map(Byte::toInt).toIntArray(),
-              mapper.toByte(), mirror, battery
-          )
-        }
-  }
-}
\ No newline at end of file
diff --git a/app/src/main/kotlin/android/emu6502/nes/PPU.kt b/app/src/main/kotlin/android/emu6502/nes/PPU.kt
deleted file mode 100644
index 25374c7..0000000
--- a/app/src/main/kotlin/android/emu6502/nes/PPU.kt
+++ /dev/null
@@ -1,211 +0,0 @@
-package android.emu6502.nes
-
-import android.emu6502.shl
-import android.emu6502.shr
-import android.media.Image
-import android.system.Os.read
-import kotlin.experimental.and
-import kotlin.experimental.xor
-
-class PPU(
-    val console:                Console,
-    // @formatter:off
-
-    var cycle:                  Int = 0,            // 0-340
-    var scanLine:               Int = 0,            // 0-261, 0-239=visible, 240=post, 241-260=vblank, 261=pre
-    var frame:                  Int = 0,            // frame counter
-
-    // storage variables
-    var paletteData:            ByteArray = ByteArray(32),
-    var nameTableData:          ByteArray = ByteArray(2048),
-    var oamData:                ByteArray = ByteArray(256),
-    var front:                  Image,
-    var back:                   Image,
-
-    // PPU registers
-    var v:                      Int = 0,            // current vram address (15 bit)
-    var t:                      Int = 0,            // temporary vram address (15 bit)
-    var x:                      Byte = 0,           // fine x scroll (3 bit)
-    var w:                      Byte = 0,           // write toggle (1 bit)
-    var f:                      Byte = 0,           // even/odd frame flag (1 bit)
-    var register:               Byte = 0,
-
-    var nmiOccurred:            Boolean = false,
-    var nmiOutput:              Boolean = false,
-    var nmiPrevious:            Boolean = false,
-    var nmiDelay:               Byte = 0,
-
-    // background temporary variables
-    var nameTableByte:          Byte = 0,
-    var attributeTableByte:     Byte = 0,
-    var lowTileByte:            Byte = 0,
-    var highTileByte:           Byte = 0,
-    var tileData:               Int = 0,
-
-    // $2000 PPUCTRL
-    var flagNameTable:          Byte = 0, // 0: $2000; 1: $2400; 2: $2800; 3: $2C00
-    var flagIncrement:          Byte = 0, // 0: add 1; 1: add 32
-    var flagSpriteTable:        Byte = 0, // 0: $0000; 1: $1000; ignored in 8x16 mode
-    var flagBackgroundTable:    Byte = 0, // 0: $0000; 1: $1000
-    var flagSpriteSize:         Byte = 0, // 0: 8x8; 1: 8x16
-    var flagMasterSlave:        Byte = 0, // 0: read EXT; 1: write EXT
-
-    // $2001 PPUMASK
-    var flagGrayscale:          Byte = 0, // 0: color; 1: grayscale
-    var flagShowLeftBackground: Byte = 0, // 0: hide; 1: show
-    var flagShowLeftSprites:    Byte = 0, // 0: hide; 1: show
-    var flagShowBackground:     Byte = 0, // 0: hide; 1: show
-    var flagShowSprites:        Byte = 0, // 0: hide; 1: show
-    var flagRedTint:            Byte = 0, // 0: normal; 1: emphasized
-    var flagGreenTint:          Byte = 0, // 0: normal; 1: emphasized
-    var flagBlueTint:           Byte = 0, // 0: normal; 1: emphasized
-
-    // $2002 PPUSTATUS
-    val flagSpriteZeroHit:      Boolean = false,
-    val flagSpriteOverflow:     Boolean = false,
-
-    // $2003 OAMADDR
-    var oamAddress:             Byte = 0,
-
-    // $2007 PPUDATA
-    val bufferedData:           Byte = 0 // for buffered reads
-
-    // @formatter:on
-) {
-  fun writeRegister(address: Int, value: Byte) {
-    register = value
-    when (address) {
-      0x2000 -> writeControl(value)
-      0x2001 -> writeMask(value)
-      0x2003 -> writeOAMAddress(value)
-      0x2004 -> writeOAMData(value)
-      0x2005 -> writeScroll(value)
-      0x2006 -> writeAddress(value)
-      0x2007 -> writeData(value)
-      0x4014 -> writeDMA(value)
-    }
-  }
-
-  private fun writeDMA(value: Byte) {
-    TODO()
-  }
-
-  private fun step() {
-    tick()
-    val renderingEnabled = flagShowBackground != 0.toByte() || flagShowSprites != 0.toByte()
-    val preLine = scanLine == 261
-    val visibleLine = scanLine < 240
-    // postLine = scanLine == 240
-    val renderLine = preLine || visibleLine
-    val preFetchCycle = cycle in 321..336
-    val visibleCycle = cycle in 1..256
-    val fetchCycle = preFetchCycle || visibleCycle
-  }
-
-  private fun tick() {
-    if (nmiDelay > 0) {
-      nmiDelay--
-      if (nmiDelay == 0.toByte() && nmiOutput && nmiOccurred) {
-        console.cpu.triggerNMI()
-      }
-    }
-
-    if (flagShowBackground != 0.toByte() || flagShowSprites != 0.toByte()) {
-      if (f == 1.toByte() && scanLine == 261 && cycle == 339) {
-        cycle = 0
-        scanLine = 0
-        frame++
-        f = f xor 1
-        return
-      }
-    }
-    cycle++
-    if (cycle > 340) {
-      cycle = 0
-      scanLine++
-      if (scanLine > 261) {
-        scanLine = 0
-        frame++
-        f = f xor 1
-      }
-    }
-  }
-
-  private fun writeData(value: Byte) {
-    TODO("not implemented")
-  }
-
-  // $2006: PPUADDR
-  private fun writeAddress(value: Byte) {
-    if (w == 0.toByte()) {
-      // t: ..FEDCBA ........ = d: ..FEDCBA
-      // t: .X...... ........ = 0
-      // w:                   = 1
-      t = (t and 0x80FF) or ((value and 0x3F) shl 8).toInt()
-      w = 1
-    } else {
-      // t: ........ HGFEDCBA = d: HGFEDCBA
-      // v                    = t
-      // w:                   = 0
-      t = (t and 0xFF00) or value.toInt()
-      v = t
-      w = 0
-    }
-  }
-
-  // $2005: PPUSCROLL
-  private fun writeScroll(value: Byte) {
-    TODO("not implemented")
-  }
-
-  // $2004: OAMDATA (write)
-  private fun writeOAMData(value: Byte) {
-    oamData[oamAddress.toInt()] = value
-    oamAddress++
-  }
-
-  // $2003: OAMADDR
-  private fun writeOAMAddress(value: Byte) {
-    oamAddress = value
-  }
-
-  private fun writeMask(value: Byte) {
-    flagGrayscale = (value shr 0) and 1
-    flagShowLeftBackground = (value shr 1) and 1
-    flagShowLeftSprites = (value shr 2) and 1
-    flagShowBackground = (value shr 3) and 1
-    flagShowSprites = (value shr 4) and 1
-    flagRedTint = (value shr 5) and 1
-    flagGreenTint = (value shr 6) and 1
-    flagBlueTint = (value shr 7) and 1
-  }
-
-  // $2000: PPUCTRL
-  private fun writeControl(value: Byte) {
-    flagNameTable = (value shr 0) and 3
-    flagIncrement = (value shr 2) and 1
-    flagSpriteTable = (value shr 3) and 1
-    flagBackgroundTable = (value shr 4) and 1
-    flagSpriteSize = (value shr 5) and 1
-    flagMasterSlave = (value shr 6) and 1
-    nmiOutput = (value shr 7) and 1 == 1.toByte()
-    nmiChange()
-    // t: ....BA.. ........ = d: ......BA
-    t = (t and 0xF3FF) or ((value and 0x03) shl 10).toInt()
-  }
-
-  private fun nmiChange() {
-    val nmi = nmiOutput && nmiOccurred
-    if (nmi && !nmiPrevious) {
-      // TODO: this fixes some games but the delay shouldn't have to be so
-      // long, so the timings are off somewhere
-      nmiDelay = 15
-    }
-    nmiPrevious = nmi
-  }
-
-  private fun fetchNameTableByte() {
-    val address = 0x2000 or (v and 0x0FFF)
-    nameTableByte = read(address)
-  }
-}
\ No newline at end of file
diff --git a/app/src/main/kotlin/android/emu6502/nes/mappers/AOROM.kt b/app/src/main/kotlin/android/emu6502/nes/mappers/AOROM.kt
deleted file mode 100644
index 7c300dc..0000000
--- a/app/src/main/kotlin/android/emu6502/nes/mappers/AOROM.kt
+++ /dev/null
@@ -1,13 +0,0 @@
-package android.emu6502.nes.mappers
-
-class AOROM : Mapper {
-  override fun write(address: Int, value: Int) {
-  }
-
-  override fun step() {
-  }
-
-  override fun read(address: Int): Int {
-    throw NotImplementedError()
-  }
-}
\ No newline at end of file
diff --git a/app/src/main/kotlin/android/emu6502/nes/mappers/CNROM.kt b/app/src/main/kotlin/android/emu6502/nes/mappers/CNROM.kt
deleted file mode 100644
index e61fcbc..0000000
--- a/app/src/main/kotlin/android/emu6502/nes/mappers/CNROM.kt
+++ /dev/null
@@ -1,13 +0,0 @@
-package android.emu6502.nes.mappers
-
-class CNROM : Mapper  {
-  override fun write(address: Int, value: Int) {
-  }
-
-  override fun step() {
-  }
-
-  override fun read(address: Int): Int {
-    throw NotImplementedError()
-  }
-}
\ No newline at end of file
diff --git a/app/src/main/kotlin/android/emu6502/nes/mappers/MMC1.kt b/app/src/main/kotlin/android/emu6502/nes/mappers/MMC1.kt
deleted file mode 100644
index 9304432..0000000
--- a/app/src/main/kotlin/android/emu6502/nes/mappers/MMC1.kt
+++ /dev/null
@@ -1,13 +0,0 @@
-package android.emu6502.nes.mappers
-
-class MMC1 : Mapper  {
-  override fun write(address: Int, value: Int) {
-  }
-
-  override fun step() {
-  }
-
-  override fun read(address: Int): Int {
-    throw NotImplementedError()
-  }
-}
\ No newline at end of file
diff --git a/app/src/main/kotlin/android/emu6502/nes/mappers/MMC3.kt b/app/src/main/kotlin/android/emu6502/nes/mappers/MMC3.kt
deleted file mode 100644
index cd9e344..0000000
--- a/app/src/main/kotlin/android/emu6502/nes/mappers/MMC3.kt
+++ /dev/null
@@ -1,214 +0,0 @@
-package android.emu6502.nes.mappers
-
-import android.emu6502.CPU
-import android.emu6502.nes.Cartridge
-import android.emu6502.nes.PPU
-import android.emu6502.toHexString
-
-// http://wiki.nesdev.com/w/index.php/MMC3
-class MMC3(
-    private val cartridge: Cartridge,
-    private val ppu: PPU,
-    private val cpu: CPU
-) : Mapper {
-  private var register: Int = 0
-  private var registers = IntArray(8)
-  private var prgMode: Int = 0
-  private var chrMode: Int = 0
-  private var prgOffsets = IntArray(4)
-  private var chrOffsets = IntArray(8)
-  private var reload: Int = 0
-  private var counter: Int = 0
-  private var irqEnable: Boolean = false
-
-  override fun read(address: Int): Int {
-    return when {
-      address < 0x2000 -> {
-        val bank = address / 0x0400
-        val offset = address % 0x0400
-        cartridge.chr[chrOffsets[bank] + offset]
-      }
-      address >= 0x8000 -> {
-        val addr = address - 0x8000
-        val bank = addr / 0x2000
-        val offset = addr % 0x2000
-        cartridge.pgr[prgOffsets[bank] + offset]
-      }
-      address >= 0x6000 -> {
-        return cartridge.sram[address - 0x6000]
-      }
-      else -> throw RuntimeException("unhandled mapper4 read at address: ${address.toHexString()}")
-    }
-  }
-
-  override fun write(address: Int, value: Int) {
-    when {
-      address < 0x2000 -> {
-        val bank = address / 0x0400
-        val offset = address % 0x0400
-        cartridge.chr[chrOffsets[bank] + offset] = value
-      }
-      address >= 0x8000 -> {
-        writeRegister(address, value)
-      }
-      address >= 0x6000 -> {
-        cartridge.sram[address - 0x6000] = value
-      }
-      else -> throw RuntimeException("unhandled mapper4 write at address ${address.toHexString()}")
-    }
-  }
-
-  private fun writeRegister(address: Int, value: Int) {
-    if (address <= 0x9FFF && address % 2 == 0)
-      writeBankSelect(value)
-    else if (address <= 0x9FFF && address % 2 == 1)
-      writeBankData(value)
-    else if (address <= 0xBFFF && address % 2 == 0)
-      writeMirror(value)
-    else if (address <= 0xBFFF && address % 2 == 1)
-      writeProtect()
-    else if (address <= 0xDFFF && address % 2 == 0)
-      writeIRQLatch(value)
-    else if (address <= 0xDFFF && address % 2 == 1)
-      writeIRQReload()
-    else if (address <= 0xFFFF && address % 2 == 0)
-      writeIRQDisable()
-    else if (address <= 0xFFFF && address % 2 == 1)
-      writeIRQEnable()
-  }
-
-  private fun writeBankSelect(value: Int) {
-    prgMode = (value shr 6) and 1
-    chrMode = (value shr 7) and 1
-    register = value and 7
-    updateOffsets()
-  }
-
-  private fun updateOffsets() {
-    when (prgMode) {
-      0 -> {
-        prgOffsets[0] = prgBankOffset(registers[6])
-        prgOffsets[1] = prgBankOffset(registers[7])
-        prgOffsets[2] = prgBankOffset(-2)
-        prgOffsets[3] = prgBankOffset(-1)
-      }
-      1 -> {
-        prgOffsets[0] = prgBankOffset(-2)
-        prgOffsets[1] = prgBankOffset(registers[7])
-        prgOffsets[2] = prgBankOffset(registers[6])
-        prgOffsets[3] = prgBankOffset(-1)
-      }
-    }
-    when (chrMode) {
-      0 -> {
-        chrOffsets[0] = chrBankOffset(registers[0] and 0xFE)
-        chrOffsets[1] = chrBankOffset(registers[0] or 0x01)
-        chrOffsets[2] = chrBankOffset(registers[1] and 0xFE)
-        chrOffsets[3] = chrBankOffset(registers[1] or 0x01)
-        chrOffsets[4] = chrBankOffset(registers[2])
-        chrOffsets[5] = chrBankOffset(registers[3])
-        chrOffsets[6] = chrBankOffset(registers[4])
-        chrOffsets[7] = chrBankOffset(registers[5])
-      }
-      1 -> {
-        chrOffsets[0] = chrBankOffset(registers[2])
-        chrOffsets[1] = chrBankOffset(registers[3])
-        chrOffsets[2] = chrBankOffset(registers[4])
-        chrOffsets[3] = chrBankOffset(registers[5])
-        chrOffsets[4] = chrBankOffset(registers[0] and 0xFE)
-        chrOffsets[5] = chrBankOffset(registers[0] or 0x01)
-        chrOffsets[6] = chrBankOffset(registers[1] and 0xFE)
-        chrOffsets[7] = chrBankOffset(registers[1] or 0x01)
-      }
-    }
-  }
-
-  private fun chrBankOffset(index: Int): Int {
-    var idx = index
-    if (idx >= 0x80) {
-      idx -= 0x100
-    }
-    idx %= cartridge.chr.size / 0x0400
-    var offset = idx * 0x0400
-    if (offset < 0) {
-      offset += cartridge.chr.size
-    }
-    return offset
-  }
-
-  private fun prgBankOffset(index: Int): Int {
-    var idx = index
-    if (idx >= 0x80) {
-      idx -= 0x100
-    }
-    idx %= cartridge.chr.size / 0x2000
-    var offset = idx * 0x2000
-    if (offset < 0) {
-      offset += cartridge.chr.size
-    }
-    return offset
-  }
-
-  private fun writeBankData(value: Int) {
-    registers[register] = value
-    updateOffsets()
-  }
-
-  private fun writeMirror(value: Int) {
-    when (value and 1) {
-      0 -> cartridge.mirror = MirrorVertical
-      1 -> cartridge.mirror = MirrorHorizontal
-    }
-  }
-
-  private fun writeProtect() {
-  }
-
-  private fun writeIRQLatch(value: Int) {
-    reload = value
-  }
-
-  private fun writeIRQReload() {
-    counter = 0
-  }
-
-  private fun writeIRQDisable() {
-    irqEnable = false
-  }
-
-  private fun writeIRQEnable() {
-    irqEnable = true
-  }
-
-  override fun step() {
-    if (ppu.cycle != 280) { // TODO: this *should* be 260
-      return
-    }
-    if (ppu.scanLine in 240..260) {
-      return
-    }
-    if (!ppu.flagShowBackground && !ppu.flagShowSprites) {
-      return
-    }
-    handleScanLine()
-  }
-
-  private fun handleScanLine() {
-    if (counter == 0) {
-      counter = reload
-    } else {
-      counter--
-      if (counter == 0 && irqEnable) {
-        cpu.triggerIRQ()
-      }
-    }
-  }
-
-  companion object {
-    val MirrorHorizontal = 0
-    val MirrorVertical = 1
-    val MirrorSingle0 = 2
-    val MirrorSingle1 = 3
-    val MirrorFour = 4
-  }
-}
\ No newline at end of file
diff --git a/app/src/main/kotlin/android/emu6502/nes/mappers/Mapper.kt b/app/src/main/kotlin/android/emu6502/nes/mappers/Mapper.kt
deleted file mode 100644
index abce61a..0000000
--- a/app/src/main/kotlin/android/emu6502/nes/mappers/Mapper.kt
+++ /dev/null
@@ -1,19 +0,0 @@
-package android.emu6502.nes.mappers
-
-import android.emu6502.CPU
-import android.emu6502.nes.Cartridge
-import android.emu6502.nes.PPU
-
-interface Mapper {
-  fun read(address: Int): Int
-  fun write(address: Int, value: Int)
-  fun step()
-
-  companion object {
-    fun newMapper(cartridge: Cartridge, ppu: PPU, cpu: CPU): Mapper =
-        when (cartridge.mapper.toInt()) {
-          4 -> MMC3(cartridge, ppu, cpu)
-          else -> throw NotImplementedError("Mapper ${cartridge.mapper.toInt()} not implemented")
-        }
-  }
-}
\ No newline at end of file
diff --git a/app/src/main/kotlin/android/emu6502/nes/mappers/UNROM.kt b/app/src/main/kotlin/android/emu6502/nes/mappers/UNROM.kt
deleted file mode 100644
index 87de66c..0000000
--- a/app/src/main/kotlin/android/emu6502/nes/mappers/UNROM.kt
+++ /dev/null
@@ -1,13 +0,0 @@
-package android.emu6502.nes.mappers
-
-class UNROM : Mapper  {
-  override fun write(address: Int, value: Int) {
-  }
-
-  override fun step() {
-  }
-
-  override fun read(address: Int): Int {
-    throw NotImplementedError()
-  }
-}
\ No newline at end of file
diff --git a/build.gradle b/build.gradle
index 57ead14..90eb290 100644
--- a/build.gradle
+++ b/build.gradle
@@ -6,8 +6,8 @@ buildscript {
     google()
   }
   dependencies {
-    classpath 'com.android.tools.build:gradle:3.1.4'
-    classpath 'org.jetbrains.kotlin:kotlin-gradle-plugin:1.2.60'
+    classpath 'com.android.tools.build:gradle:3.3.0-alpha08'
+    classpath 'org.jetbrains.kotlin:kotlin-gradle-plugin:1.2.61'
 
     // NOTE: Do not place your application dependencies here; they belong
     // in the individual module build.gradle files
diff --git a/gradle/wrapper/gradle-wrapper.properties b/gradle/wrapper/gradle-wrapper.properties
index 9f01edc..a1a45ac 100644
--- a/gradle/wrapper/gradle-wrapper.properties
+++ b/gradle/wrapper/gradle-wrapper.properties
@@ -3,4 +3,4 @@ distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-4.5-all.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-4.9-all.zip