@@ -114,8 +114,23 @@ break;
 	}
 }
 
+static inline size_t _tileId(struct mMapCache* cache, unsigned x, unsigned y) {
+	int tilesWide = mMapCacheSystemInfoGetTilesWide(cache->sysConfig);
+	int tilesHigh = mMapCacheSystemInfoGetTilesHigh(cache->sysConfig);
+	int stride = tilesHigh < 5 ? (1 << tilesHigh) : 32;
+	x &= (1 << tilesWide) - 1;
+	y &= (1 << tilesHigh) - 1;
+	unsigned xMajor = x & ~0x1F;
+	unsigned yMajor = y >> 5;
+	x &= 0x1F;
+	y &= 0x1F;
+	yMajor <<= tilesHigh;
+	y += xMajor + yMajor;
+	return stride * y + x;
+}
+
 void mMapCacheCleanTile(struct mMapCache* cache, struct mMapCacheEntry* entry, unsigned x, unsigned y) {
-	size_t location = (1 << mMapCacheSystemInfoGetTilesWide(cache->sysConfig)) * y + x;
+	size_t location = _tileId(cache, x, y);
 	struct mMapCacheEntry* status = &cache->status[location];
 	int paletteId = mMapCacheEntryFlagsGetPaletteId(status->flags);
 	const color_t* tile = NULL;
@@ -141,7 +156,7 @@ entry[location] = *status;
 }
 
 bool mMapCacheCheckTile(struct mMapCache* cache, const struct mMapCacheEntry* entry, unsigned x, unsigned y) {
-	size_t location = (1 << mMapCacheSystemInfoGetTilesWide(cache->sysConfig)) * y + x;
+	size_t location = _tileId(cache, x, y);
 	struct mMapCacheEntry* status = &cache->status[location];
 	int paletteId = mMapCacheEntryFlagsGetPaletteId(status->flags);
 	const color_t* tile = NULL;

@@ -114,7 +114,7 @@ mMapCacheSystemInfo sysconfig = 0;
 	if (map->mapParser == mapParser0) {
 		sysconfig = mMapCacheSystemInfoSetPaletteBPP(sysconfig, 2 + p);
 		sysconfig = mMapCacheSystemInfoSetPaletteCount(sysconfig, 4 * !p);
-		sysconfig = mMapCacheSystemInfoSetMaxTiles(sysconfig, 512);
+		sysconfig = mMapCacheSystemInfoSetMaxTiles(sysconfig, 1024);
 		sysconfig = mMapCacheSystemInfoSetMapAlign(sysconfig, 1);
 		tilesWide = 5;
 		tilesHigh = 5;

@@ -8,7 +8,9 @@
 #include "CoreController.h"
 #include "GBAApp.h"
 
+#include <QButtonGroup>
 #include <QFontDatabase>
+#include <QRadioButton>
 #include <QTimer>
 
 using namespace QGBA;
@@ -38,19 +40,51 @@
 	connect(m_ui.magnification, static_cast<void (QSpinBox::*)(int)>(&QSpinBox::valueChanged), [this]() {
 		updateTiles(true);
 	});
+
+	CoreController::Interrupter interrupter(m_controller);
+	const mCoreChannelInfo* videoLayers;
+	size_t nVideo = m_controller->thread()->core->listVideoLayers(m_controller->thread()->core, &videoLayers);
+	QButtonGroup* group = new QButtonGroup(this);
+	for (size_t i = 0; i < nVideo; ++i) {
+		if (strncmp(videoLayers[i].internalName, "bg", 2) != 0) {
+			continue;
+		}
+		QRadioButton* button = new QRadioButton(tr(videoLayers[i].visibleName));
+		if (!i) {
+			button->setChecked(true);
+		}
+		m_ui.bgLayout->addWidget(button);
+		connect(button, &QAbstractButton::pressed, button, [this, i]() {
+			selectMap(i);
+		});
+		group->addButton(button);
+	}
+}
+
+void MapView::selectMap(int map) {
+	if (map >= mMapCacheSetSize(&m_cacheSet->maps)) {
+		return;
+	}
+	m_map = map;
 }
 
 #ifdef M_CORE_GBA
 void MapView::updateTilesGBA(bool force) {
-	QImage bg(QSize(256, 256), QImage::Format_ARGB32);
-	uchar* bgBits = bg.bits();
-	mMapCache* mapCache = mMapCacheSetGetPointer(&m_cacheSet->maps, 0);
-	for (int j = 0; j < 32; ++j) {
-		for (int i = 0; i < 32; ++i) {
-			mMapCacheCleanTile(mapCache, &m_mapStatus[i + j * 32], i, j);
-		}
-		for (int i = 0; i < 8; ++i) {
-			memcpy(static_cast<void*>(&bgBits[256 * 4 * (i + j * 8)]), mMapCacheGetRow(mapCache, i + j * 8), 256 * 4);
+	QImage bg;
+	{
+		CoreController::Interrupter interrupter(m_controller);
+		mMapCache* mapCache = mMapCacheSetGetPointer(&m_cacheSet->maps, m_map);
+		int tilesW = 1 << mMapCacheSystemInfoGetTilesWide(mapCache->sysConfig);
+		int tilesH = 1 << mMapCacheSystemInfoGetTilesHigh(mapCache->sysConfig);
+		bg = QImage(QSize(tilesW * 8, tilesH * 8), QImage::Format_ARGB32);
+		uchar* bgBits = bg.bits();
+		for (int j = 0; j < tilesH; ++j) {
+			for (int i = 0; i < tilesW; ++i) {
+				mMapCacheCleanTile(mapCache, &m_mapStatus[i + j * tilesW], i, j);
+			}
+			for (int i = 0; i < 8; ++i) {
+				memcpy(static_cast<void*>(&bgBits[tilesW * 32 * (i + j * 8)]), mMapCacheGetRow(mapCache, i + j * 8), tilesW * 32);
+			}
 		}
 	}
 	bg = bg.convertToFormat(QImage::Format_RGB32).rgbSwapped();

@@ -21,6 +21,9 @@
 public:
 	MapView(std::shared_ptr<CoreController> controller, QWidget* parent = nullptr);
 
+private slots:
+	void selectMap(int);
+
 private:
 #ifdef M_CORE_GBA
 	void updateTilesGBA(bool force) override;
@@ -33,6 +36,7 @@ Ui::MapView m_ui;
 
 	std::shared_ptr<CoreController> m_controller;
 	mMapCacheEntry m_mapStatus[1024 * 1024] = {}; // TODO: Correct size
+	int m_map = 0;
 };
 
 }

@@ -14,13 +14,13 @@ <property name="windowTitle">
    <string>Maps</string>
   </property>
   <layout class="QGridLayout" name="gridLayout">
-   <item row="1" column="0">
-    <widget class="QGBA::AssetTile" name="tile"/>
-   </item>
-   <item row="0" column="1" rowspan="3">
+   <item row="0" column="1" rowspan="4">
     <widget class="QScrollArea" name="scrollArea">
      <property name="widgetResizable">
       <bool>true</bool>
+     </property>
+     <property name="alignment">
+      <set>Qt::AlignLeading|Qt::AlignLeft|Qt::AlignTop</set>
      </property>
      <widget class="QWidget" name="scrollAreaWidgetContents">
       <property name="geometry">
@@ -44,6 +44,9 @@ </widget>
     </widget>
    </item>
    <item row="2" column="0">
+    <widget class="QGBA::AssetTile" name="tile"/>
+   </item>
+   <item row="3" column="0">
     <spacer name="verticalSpacer">
      <property name="orientation">
       <enum>Qt::Vertical</enum>
@@ -56,7 +59,7 @@ </size>
      </property>
     </spacer>
    </item>
-   <item row="0" column="0">
+   <item row="1" column="0">
     <layout class="QHBoxLayout" name="horizontalLayout_4">
      <item>
       <widget class="QSpinBox" name="magnification">
@@ -85,6 +88,9 @@ </property>
       </widget>
      </item>
     </layout>
+   </item>
+   <item row="0" column="0">
+    <layout class="QVBoxLayout" name="bgLayout"/>
    </item>
   </layout>
  </widget>