diff --git a/src/nostalgia/modules/core/include/nostalgia/core/gfx.hpp b/src/nostalgia/modules/core/include/nostalgia/core/gfx.hpp
index 90340117..ca017384 100644
--- a/src/nostalgia/modules/core/include/nostalgia/core/gfx.hpp
+++ b/src/nostalgia/modules/core/include/nostalgia/core/gfx.hpp
@@ -73,7 +73,7 @@ struct TileSheetSetEntrySection {
 
 oxModelBegin(TileSheetSetEntrySection)
 	oxModelField(begin)
-	oxModelField(size)
+	oxModelField(tiles)
 oxModelEnd()
 
 struct TileSheetSetEntry {
@@ -92,7 +92,7 @@ struct TileSheetSet {
 	static constexpr auto TypeName = "net.drinkingtea.nostalgia.core.TileSheetSet";
 	static constexpr auto TypeVersion = 1;
 	static constexpr auto Preloadable = true;
-	int bpp = 0;
+	int32_t bpp = 0;
 	ox::Vector<TileSheetSetEntry> entries;
 };
 
@@ -101,6 +101,8 @@ oxModelBegin(TileSheetSet)
 	oxModelField(entries)
 oxModelEnd()
 
+void addEntry(TileSheetSet &set, ox::FileAddress path, int32_t begin = 0, int32_t size = -1) noexcept;
+
 ox::Error loadBgPalette(
 		Context &ctx,
 		size_t palBank,
diff --git a/src/nostalgia/modules/core/include/nostalgia/core/palette.hpp b/src/nostalgia/modules/core/include/nostalgia/core/palette.hpp
index 06eba728..72f97859 100644
--- a/src/nostalgia/modules/core/include/nostalgia/core/palette.hpp
+++ b/src/nostalgia/modules/core/include/nostalgia/core/palette.hpp
@@ -60,6 +60,15 @@ constexpr size_t colors(Palette const&pal, size_t page = 0) noexcept {
 	return 0;
 }
 
+[[nodiscard]]
+constexpr size_t largestPage(Palette const&pal) noexcept {
+	size_t out{};
+	for (auto const&page : pal.pages) {
+		out = ox::max(out, page.size());
+	}
+	return out;
+}
+
 oxModelBegin(NostalgiaPalette)
 	oxModelField(colors)
 oxModelEnd()
diff --git a/src/nostalgia/modules/core/include/nostalgia/core/tilesheet.hpp b/src/nostalgia/modules/core/include/nostalgia/core/tilesheet.hpp
index 06beb9c5..3de737d1 100644
--- a/src/nostalgia/modules/core/include/nostalgia/core/tilesheet.hpp
+++ b/src/nostalgia/modules/core/include/nostalgia/core/tilesheet.hpp
@@ -159,7 +159,10 @@ struct TileSheet {
 std::size_t idx(TileSheet::SubSheet const&ss, ox::Point const&pt) noexcept;
 
 [[nodiscard]]
-TileSheet::SubSheet const*getSubsheet(TileSheet const&ts, SubSheetId const id) noexcept;
+size_t getTileCnt(TileSheet const&ts) noexcept;
+
+[[nodiscard]]
+TileSheet::SubSheet const*getSubsheet(TileSheet const&ts, SubSheetId id) noexcept;
 
 [[nodiscard]]
 size_t getTileIdx(TileSheet const&ts, SubSheetId id) noexcept;
diff --git a/src/nostalgia/modules/core/src/studio/tilesheeteditor/tilesheeteditormodel.cpp b/src/nostalgia/modules/core/src/studio/tilesheeteditor/tilesheeteditormodel.cpp
index b82a932a..7694efa9 100644
--- a/src/nostalgia/modules/core/src/studio/tilesheeteditor/tilesheeteditormodel.cpp
+++ b/src/nostalgia/modules/core/src/studio/tilesheeteditor/tilesheeteditormodel.cpp
@@ -30,6 +30,17 @@ Palette const TileSheetEditorModel::s_defaultPalette = {
 	.pages = {ox::Vector<Color16>(128)},
 };
 
+// delete pixels of all non-leaf nodes
+static void normalizeSubsheets(TileSheet::SubSheet &ss) noexcept {
+	if (ss.subsheets.empty()) {
+		for (auto &child : ss.subsheets) {
+			normalizeSubsheets(child);
+		}
+	} else {
+		ss.pixels.clear();
+	}
+}
+
 TileSheetEditorModel::TileSheetEditorModel(turbine::Context &ctx, ox::StringView path, studio::UndoStack &undoStack):
 	m_ctx(ctx),
 	m_path(path),
@@ -37,6 +48,7 @@ TileSheetEditorModel::TileSheetEditorModel(turbine::Context &ctx, ox::StringView
 	// ignore failure to load palette
 	m_pal(readObj<Palette>(keelCtx(m_ctx), m_img.defaultPalette).value),
 	m_undoStack(undoStack) {
+	normalizeSubsheets(m_img.subsheet);
 	m_pal.updated.connect(this, &TileSheetEditorModel::markUpdated);
 	m_undoStack.changeTriggered.connect(this, &TileSheetEditorModel::markUpdatedCmdId);
 }
diff --git a/src/nostalgia/modules/core/src/tilesheet.cpp b/src/nostalgia/modules/core/src/tilesheet.cpp
index 67b2c2e0..58ebc156 100644
--- a/src/nostalgia/modules/core/src/tilesheet.cpp
+++ b/src/nostalgia/modules/core/src/tilesheet.cpp
@@ -14,6 +14,7 @@ std::size_t idx(TileSheet::SubSheet const&ss, ox::Point const&pt) noexcept {
 	return ptToIdx(pt, ss.columns);
 }
 
+[[nodiscard]]
 static TileSheet::SubSheet const*getSubsheet(TileSheet::SubSheet const&ss, SubSheetId const id) noexcept {
 	if (ss.id == id) {
 		return &ss;
@@ -26,6 +27,24 @@ static TileSheet::SubSheet const*getSubsheet(TileSheet::SubSheet const&ss, SubSh
 	return {};
 }
 
+[[nodiscard]]
+static size_t getTileCnt(TileSheet::SubSheet const&ss, int const bpp) noexcept {
+	if (ss.subsheets.empty()) {
+		auto const bytesPerTile = bpp == 4 ? 32u : 64u;
+		return ss.pixels.size() / bytesPerTile;
+	} else {
+		size_t out{};
+		for (auto const&child : ss.subsheets) {
+			out += getTileCnt(child, bpp);
+		}
+		return out;
+	}
+}
+
+size_t getTileCnt(TileSheet const&ts) noexcept {
+	return getTileCnt(ts.subsheet, ts.bpp);
+}
+
 TileSheet::SubSheet const*getSubsheet(TileSheet const&ts, SubSheetId const id) noexcept {
 	return getSubsheet(ts.subsheet, id);
 }
@@ -42,7 +61,7 @@ static ox::Optional<size_t> getPixelIdx(
 		if (auto out = getPixelIdx(child, id, idx, bpp)) {
 			return out;
 		}
-		idx += pixelCnt(ss, bpp);
+		idx += pixelCnt(child, bpp);
 	}
 	return {};
 }
diff --git a/src/olympic/keel/include/keel/assetmanager.hpp b/src/olympic/keel/include/keel/assetmanager.hpp
index 39c3a07f..f27667f1 100644
--- a/src/olympic/keel/include/keel/assetmanager.hpp
+++ b/src/olympic/keel/include/keel/assetmanager.hpp
@@ -284,10 +284,6 @@ class AssetRef {
 			return *m_obj;
 		}
 
-		constexpr T const&&operator*() const && noexcept {
-			return *m_obj;
-		}
-
 		constexpr T const*operator->() const noexcept {
 			return m_obj;
 		}