diff --git a/deps/ox/src/ox/std/CMakeLists.txt b/deps/ox/src/ox/std/CMakeLists.txt
index 32cdf7c..0c1ad78 100644
--- a/deps/ox/src/ox/std/CMakeLists.txt
+++ b/deps/ox/src/ox/std/CMakeLists.txt
@@ -113,6 +113,7 @@ install(
 		memory.hpp
 		new.hpp
 		optional.hpp
+		pair.hpp
 		point.hpp
 		random.hpp
 		ranges.hpp
diff --git a/deps/ox/src/ox/std/conv.hpp b/deps/ox/src/ox/std/conv.hpp
index 4329f86..f17e69f 100644
--- a/deps/ox/src/ox/std/conv.hpp
+++ b/deps/ox/src/ox/std/conv.hpp
@@ -14,32 +14,20 @@
 
 namespace ox {
 
-constexpr Vec2::operator Point() const noexcept {
-	return {
-			static_cast<int32_t>(x),
-			static_cast<int32_t>(y),
-	};
-}
+constexpr Point::Point(Vec2 const&pt) noexcept:
+	x(static_cast<int32_t>(pt.x)),
+	y(static_cast<int32_t>(pt.y)) {}
 
-constexpr Vec2::operator Size() const noexcept {
-	return {
-			static_cast<int32_t>(x),
-			static_cast<int32_t>(y),
-	};
-}
+constexpr Size::Size(Vec2 const&pt) noexcept:
+	width(static_cast<int32_t>(pt.x)),
+	height(static_cast<int32_t>(pt.y)) {}
 
-constexpr Point::operator Vec2() const noexcept {
-	return {
-			static_cast<float>(x),
-			static_cast<float>(y),
-	};
-}
+constexpr Vec2::Vec2(Point const&pt) noexcept:
+		x(static_cast<float>(pt.x)),
+		y(static_cast<float>(pt.y)) {}
 
-constexpr Size::operator Vec2() const noexcept {
-	return {
-		static_cast<float>(width),
-		static_cast<float>(height),
-	};
-}
+constexpr Vec2::Vec2(Size const&pt) noexcept:
+	x(static_cast<float>(pt.width)),
+	y(static_cast<float>(pt.height)) {}
 
 }
\ No newline at end of file
diff --git a/deps/ox/src/ox/std/pair.hpp b/deps/ox/src/ox/std/pair.hpp
new file mode 100644
index 0000000..d7424de
--- /dev/null
+++ b/deps/ox/src/ox/std/pair.hpp
@@ -0,0 +1,19 @@
+/*
+ * Copyright 2015 - 2024 gary@drinkingtea.net
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#pragma once
+
+namespace ox {
+
+template<typename T, typename U = T>
+struct Pair {
+	T a{};
+	U b{};
+};
+
+}
\ No newline at end of file
diff --git a/deps/ox/src/ox/std/point.hpp b/deps/ox/src/ox/std/point.hpp
index 94062e1..57737f8 100644
--- a/deps/ox/src/ox/std/point.hpp
+++ b/deps/ox/src/ox/std/point.hpp
@@ -24,6 +24,8 @@ class Point {
 
 		constexpr Point(int x, int y) noexcept;
 
+		explicit constexpr Point(class Vec2 const&pt) noexcept;
+
 		constexpr Point operator+(const Point &p) const noexcept;
 
 		constexpr Point operator-(const Point &p) const noexcept;
diff --git a/deps/ox/src/ox/std/size.hpp b/deps/ox/src/ox/std/size.hpp
index 6684008..b2980ed 100644
--- a/deps/ox/src/ox/std/size.hpp
+++ b/deps/ox/src/ox/std/size.hpp
@@ -24,6 +24,8 @@ class Size {
 
 		constexpr Size(int width, int height) noexcept;
 
+		explicit constexpr Size(class Vec2 const&pt) noexcept;
+
 		constexpr Size operator+(Size p) const noexcept;
 
 		constexpr Size operator-(Size p) const noexcept;
diff --git a/deps/ox/src/ox/std/span.hpp b/deps/ox/src/ox/std/span.hpp
index 542ac6d..9c8bb2a 100644
--- a/deps/ox/src/ox/std/span.hpp
+++ b/deps/ox/src/ox/std/span.hpp
@@ -228,6 +228,10 @@ class Span {
 			return iterator<const T&, const T*, true>(m_items, MaxValue<size_type>, m_size);
 		}
 
+		constexpr T &operator[](std::size_t i) noexcept {
+			return m_items[i];
+		}
+
 		constexpr const T &operator[](std::size_t i) const noexcept {
 			return m_items[i];
 		}
diff --git a/deps/ox/src/ox/std/std.hpp b/deps/ox/src/ox/std/std.hpp
index a88416d..85cbc87 100644
--- a/deps/ox/src/ox/std/std.hpp
+++ b/deps/ox/src/ox/std/std.hpp
@@ -35,6 +35,7 @@
 #include "memory.hpp"
 #include "new.hpp"
 #include "optional.hpp"
+#include "pair.hpp"
 #include "point.hpp"
 #include "random.hpp"
 #include "realstd.hpp"
diff --git a/deps/ox/src/ox/std/vec.hpp b/deps/ox/src/ox/std/vec.hpp
index 22a78ad..3c443d4 100644
--- a/deps/ox/src/ox/std/vec.hpp
+++ b/deps/ox/src/ox/std/vec.hpp
@@ -142,6 +142,10 @@ class Vec2 {
 
 		constexpr Vec2() noexcept = default;
 
+		explicit constexpr Vec2(class Point const&pt) noexcept;
+
+		explicit constexpr Vec2(class Size const&pt) noexcept;
+
 		template<typename ...Args>
 		constexpr Vec2(float pX, float pY) noexcept: x(pX), y(pY) {
 		}
diff --git a/developer-handbook.md b/developer-handbook.md
index 1bb1097..e73858e 100644
--- a/developer-handbook.md
+++ b/developer-handbook.md
@@ -265,7 +265,7 @@ ox::Error engineCode() noexcept {
 	auto [val, err] = foo(1);
 	oxReturnError(err);
 	doStuff(val);
-	return OxError(0);
+	return {};
 }
 
 void anyCode() {
@@ -288,7 +288,7 @@ ox::Error engineCode() noexcept {
 	auto valerr = foo(1);
 	oxReturnError(valerr);
 	doStuff(valerr.value);
-	return OxError(0);
+	return {};
 }
 ```
 
@@ -426,7 +426,7 @@ constexpr ox::Error model(T *h, ox::CommonPtrWith<NostalgiaPalette> auto *pal) n
 	// it is also possible to provide the type name and type version as function arguments
 	//h->setTypeInfo("net.drinkingtea.nostalgia.core.NostalgiaPalette", 1);
 	oxReturnError(h->field("colors", &pal->colors));
-	return OxError(0);
+	return {};
 }
 
 template<typename T>
@@ -438,7 +438,7 @@ constexpr ox::Error model(T *h, ox::CommonPtrWith<NostalgiaGraphic> auto *ng) no
 	oxReturnError(h->field("defaultPalette", &ng->defaultPalette));
 	oxReturnError(h->field("pal", &ng->pal));
 	oxReturnError(h->field("pixels", &ng->pixels));
-	return OxError(0);
+	return {};
 }
 ```
 
@@ -475,7 +475,7 @@ constexpr Error model(T *h, ox::CommonPtrWith<FileAddress::Data> auto *obj) noex
 	oxReturnError(h->fieldCString("path", &obj->path));
 	oxReturnError(h->fieldCString("constPath", &obj->path));
 	oxReturnError(h->field("inode", &obj->inode));
-	return OxError(0);
+	return {};
 }
 
 template<typename T>
@@ -492,7 +492,7 @@ constexpr Error model(T *io, ox::CommonPtrWith<FileAddress> auto *fa) noexcept {
 		fa->m_type = static_cast<FileAddressType>(type);
 		oxReturnError(io->field("data", UnionView(&fa->m_data, static_cast<int>(fa->m_type))));
 	}
-	return OxError(0);
+	return {};
 }
 
 ```
diff --git a/src/nostalgia/modules/core/include/nostalgia/core/gfx.hpp b/src/nostalgia/modules/core/include/nostalgia/core/gfx.hpp
index 37974d6..0e104b2 100644
--- a/src/nostalgia/modules/core/include/nostalgia/core/gfx.hpp
+++ b/src/nostalgia/modules/core/include/nostalgia/core/gfx.hpp
@@ -11,6 +11,7 @@
 
 #include "context.hpp"
 #include "palette.hpp"
+#include "tilesheet.hpp"
 
 namespace nostalgia::core {
 
@@ -134,12 +135,23 @@ ox::Error loadBgTileSheet(
 		unsigned cbb,
 		TileSheetSet const&set) noexcept;
 
+ox::Error loadBgTileSheet(
+		Context &ctx,
+		unsigned cbb,
+		CompactTileSheet const&ts,
+		ox::Optional<unsigned> const&paletteBank) noexcept;
+
 ox::Error loadBgTileSheet(
 		Context &ctx,
 		unsigned cbb,
 		ox::FileAddress const&tilesheetAddr,
 		ox::Optional<unsigned> const&paletteBank = {}) noexcept;
 
+ox::Error loadSpriteTileSheet(
+		Context &ctx,
+		CompactTileSheet const&ts,
+		bool loadDefaultPalette) noexcept;
+
 ox::Error loadSpriteTileSheet(
 		Context &ctx,
 		ox::FileAddress const&tilesheetAddr,
diff --git a/src/nostalgia/modules/core/include/nostalgia/core/palette.hpp b/src/nostalgia/modules/core/include/nostalgia/core/palette.hpp
index 99149e6..af61225 100644
--- a/src/nostalgia/modules/core/include/nostalgia/core/palette.hpp
+++ b/src/nostalgia/modules/core/include/nostalgia/core/palette.hpp
@@ -74,6 +74,15 @@ constexpr bool valid(Palette const&p) noexcept {
 	});
 }
 
+[[nodiscard]]
+constexpr ox::Error repair(Palette &p) noexcept {
+	auto const colors = p.colorInfo.size();
+	for (auto &page : p.pages) {
+		page.resize(colors);
+	}
+	return {};
+}
+
 [[nodiscard]]
 constexpr Color16 color(Palette const&pal, size_t page, size_t idx) noexcept {
 	if (page < pal.pages.size() && idx < pal.pages[page].size()) [[likely]] {
diff --git a/src/nostalgia/modules/core/include/nostalgia/core/tilesheet.hpp b/src/nostalgia/modules/core/include/nostalgia/core/tilesheet.hpp
index cf7998c..a1012dc 100644
--- a/src/nostalgia/modules/core/include/nostalgia/core/tilesheet.hpp
+++ b/src/nostalgia/modules/core/include/nostalgia/core/tilesheet.hpp
@@ -296,9 +296,10 @@ using TileSheetV4 = TileSheet;
 struct CompactTileSheetV1 {
 	static constexpr auto TypeName = "net.drinkingtea.nostalgia.core.CompactTileSheet";
 	static constexpr auto TypeVersion = 1;
+	static constexpr auto Preloadable = true;
 	int8_t bpp = 0;
 	ox::FileAddress defaultPalette;
-	ox::Vector<uint8_t> pixels = {};
+	ox::Vector<uint8_t> pixels;
 };
 
 using CompactTileSheet = CompactTileSheetV1;
diff --git a/src/nostalgia/modules/core/src/gba/gfx.cpp b/src/nostalgia/modules/core/src/gba/gfx.cpp
index fb73866..553cbab 100644
--- a/src/nostalgia/modules/core/src/gba/gfx.cpp
+++ b/src/nostalgia/modules/core/src/gba/gfx.cpp
@@ -24,104 +24,6 @@ namespace nostalgia::core {
 
 constexpr auto SpriteCount = 128;
 
-struct GbaTileMapTarget {
-	static constexpr auto TypeName = CompactTileSheet::TypeName;
-	static constexpr auto TypeVersion = CompactTileSheet::TypeVersion;
-	unsigned &bpp;
-	ox::FileAddress defaultPalette;
-	volatile uint16_t *tileMap = nullptr;
-	// the following values are not actually in CompactTileSheet,
-	// and only exist to communicate with the loading process
-	size_t tileWriteIdx = 0;
-	unsigned targetBpp = 0;
-	TileSheetSetEntry const*setEntry = nullptr;
-};
-
-[[nodiscard]]
-static bool loadPixel(TileSheetSetEntry const&setEntry, size_t &sectionIdx, int tileIdx) noexcept {
-	if (setEntry.sections.size() <= sectionIdx) {
-		return false;
-	}
-	auto &section = setEntry.sections[sectionIdx];
-	if (tileIdx < section.begin) {
-		return false;
-	}
-	if (tileIdx > section.end()) {
-		if (sectionIdx >= setEntry.sections.size()) {
-			return false;
-		}
-		++sectionIdx;
-		return tileIdx > section.begin && tileIdx <= section.end();
-	}
-	return true;
-}
-
-constexpr ox::Error model(auto *io, ox::CommonPtrWith<GbaTileMapTarget> auto *t) noexcept {
-	oxReturnError(io->template setTypeInfo<CompactTileSheet>());
-	oxReturnError(io->field("bpp", &t->bpp));
-	oxReturnError(io->field("defaultPalette", &t->defaultPalette));
-	if (t->targetBpp == 0) {
-		t->targetBpp = t->bpp;
-	}
-	if (t->targetBpp != t->bpp && t->bpp == 8) {
-		return OxError(1, "Cannot load an 8 BPP tilesheet into a 4 BPP CBB");
-	}
-	ox::Error out{};
-	if (t->setEntry) {
-		// The following code is atrocious, but it works.
-		// It might be possible to clean it up a little, but it probably
-		// cannot be seriously optimized without preloading TileSheets.
-		size_t sectionIdx = 0;
-		if (t->targetBpp == t->bpp) {
-			uint16_t intermediate = 0;
-			size_t const fourBpp = t->bpp == 4;
-			const auto handleTileMap = [t, &intermediate, &sectionIdx, fourBpp]
-					(std::size_t i, uint8_t const*tile) {
-				auto const tileIdx = static_cast<int>((i * (2 * fourBpp)) / PixelsPerTile);
-				if (!loadPixel(*t->setEntry, sectionIdx, tileIdx)) {
-					return ox::Error{};
-				}
-				if (i & 1) { // i is odd
-					intermediate |= static_cast<uint16_t>(*tile) << 8;
-					t->tileMap[t->tileWriteIdx] = intermediate;
-					++t->tileWriteIdx;
-				} else { // i is even
-					intermediate = *tile & 0x00ff;
-				}
-				return ox::Error{};
-			};
-			out = io->template field<uint8_t, decltype(handleTileMap)>("tileMap", handleTileMap);
-		} else if (t->targetBpp > t->bpp) { // 4 -> 8 bits
-			const auto handleTileMap = [t, &sectionIdx](std::size_t i, uint8_t const*tile) {
-				auto constexpr BytesPerTile4Bpp = 32;
-				auto const tileIdx = static_cast<int>(i / BytesPerTile4Bpp);
-				if (!loadPixel(*t->setEntry, sectionIdx, tileIdx)) {
-					return ox::Error{};
-				}
-				uint16_t const px1 = *tile & 0xf;
-				uint16_t const px2 = *tile >> 4;
-				t->tileMap[t->tileWriteIdx] = static_cast<uint16_t>(px1 | (px2 << 8));
-				++t->tileWriteIdx;
-				return ox::Error{};
-			};
-			out = io->template field<uint8_t, decltype(handleTileMap)>("tileMap", handleTileMap);
-		}
-	} else {
-		uint16_t intermediate = 0;
-		const auto handleTileMap = [t, &intermediate](std::size_t i, const uint8_t*tile) {
-			if (i & 1) { // i is odd
-				intermediate |= static_cast<uint16_t>(*tile) << 8;
-				t->tileMap[i / 2] = intermediate;
-			} else { // i is even
-				intermediate = *tile & 0x00ff;
-			}
-			return ox::Error{};
-		};
-		out = io->template field<uint8_t, decltype(handleTileMap)>("tileMap", handleTileMap);
-	}
-	return out;
-}
-
 ox::Error initGfx(Context&, InitParams const&) noexcept {
 	for (auto bgCtl = &REG_BG0CTL; bgCtl <= &REG_BG3CTL; bgCtl += 2) {
 		teagba::bgSetSbb(*bgCtl, 28);
@@ -181,21 +83,48 @@ static ox::Error loadTileSheetSet(
 		Context &ctx,
 		uint16_t *tileMapTargetMem,
 		TileSheetSet const&set) noexcept {
-	auto &rom = ctx.rom();
 	size_t tileWriteIdx = 0;
 	for (auto const&entry : set.entries) {
-		oxRequire(tsStat, rom.stat(entry.tilesheet));
-		oxRequire(ts, rom.directAccess(entry.tilesheet));
-		unsigned tilesheetBpp{};
-		GbaTileMapTarget target{
-			.bpp = tilesheetBpp,
-			.defaultPalette = {},
-			.tileMap = tileMapTargetMem + tileWriteIdx,
-			.targetBpp = static_cast<unsigned>(set.bpp),
-			.setEntry = &entry,
-		};
-		oxReturnError(ox::readMC({ts, static_cast<std::size_t>(tsStat.size)}, target));
-		tileWriteIdx += target.tileWriteIdx;
+		oxRequire(ts, keel::readObj<CompactTileSheet>(keelCtx(ctx), entry.tilesheet));
+		if (set.bpp != ts->bpp && ts->bpp == 8) {
+			return OxError(1, "cannot load an 8 BPP tilesheet into a 4 BPP CBB");
+		}
+		for (auto const&s : entry.sections) {
+			auto const cnt = (static_cast<size_t>(s.tiles) * PixelsPerTile) / (1 + (set.bpp == 4));
+			for (size_t i = 0; i < cnt; ++i) {
+				auto const srcIdx = static_cast<size_t>(s.begin) + i * 2;
+				auto const v = static_cast<uint16_t>(
+						static_cast<uint16_t>(ts->pixels[srcIdx]) |
+				        (static_cast<uint16_t>(ts->pixels[srcIdx + 1]) << 8));
+				tileMapTargetMem[tileWriteIdx + i] = v;
+			}
+			tileWriteIdx += cnt;
+		}
+	}
+	return {};
+}
+
+ox::Error loadBgTileSheet(
+		Context &ctx,
+		unsigned cbb,
+		CompactTileSheet const&ts,
+		ox::Optional<unsigned> const&paletteBank) noexcept {
+	auto const cnt = (ts.pixels.size() * PixelsPerTile) / (1 + (ts.bpp == 4));
+	for (size_t i = 0; i < cnt; ++i) {
+		auto const srcIdx = i * 2;
+		auto const p1 = static_cast<uint16_t>(ts.pixels[srcIdx]);
+		auto const p2 = static_cast<uint16_t>(ts.pixels[srcIdx + 1]);
+		MEM_BG_TILES[cbb][i] = static_cast<uint16_t>(p1 | (p2 << 8));
+	}
+	// update bpp of all bgs with the updated cbb
+	auto const bpp = ctx.cbbData[cbb].bpp;
+	teagba::iterateBgCtl([bpp, cbb](volatile BgCtl &bgCtl) {
+		if (teagba::bgCbb(bgCtl) == cbb) {
+			teagba::bgSetBpp(bgCtl, bpp);
+		}
+	});
+	if (paletteBank.has_value() && ts.defaultPalette) {
+		oxReturnError(loadBgPalette(ctx, *paletteBank, ts.defaultPalette));
 	}
 	return {};
 }
@@ -205,26 +134,8 @@ ox::Error loadBgTileSheet(
 		unsigned cbb,
 		ox::FileAddress const&tilesheetAddr,
 		ox::Optional<unsigned> const&paletteBank) noexcept {
-	auto &rom = ctx.rom();
-	oxRequire(tsStat, rom.stat(tilesheetAddr));
-	oxRequire(ts, rom.directAccess(tilesheetAddr));
-	GbaTileMapTarget target{
-		.bpp = ctx.cbbData[cbb].bpp,
-		.defaultPalette = {},
-		.tileMap = MEM_BG_TILES[cbb].data(),
-	};
-	oxReturnError(ox::readMC({ts, static_cast<std::size_t>(tsStat.size)}, target));
-	// update bpp of all bgs with the updated cbb
-	const auto bpp = ctx.cbbData[cbb].bpp;
-	teagba::iterateBgCtl([bpp, cbb](volatile BgCtl &bgCtl) {
-		if (teagba::bgCbb(bgCtl) == cbb) {
-			teagba::bgSetBpp(bgCtl, bpp);
-		}
-	});
-	if (paletteBank.has_value() && target.defaultPalette) {
-		oxReturnError(loadBgPalette(ctx, *paletteBank, target.defaultPalette));
-	}
-	return {};
+	oxRequire(ts, keel::readObj<CompactTileSheet>(keelCtx(ctx), tilesheetAddr));
+	return loadBgTileSheet(ctx, cbb, *ts, paletteBank);
 }
 
 ox::Error loadBgTileSheet(
@@ -252,25 +163,28 @@ static void setSpritesBpp(unsigned const bpp) noexcept {
 	}
 }
 
+ox::Error loadSpriteTileSheet(
+		Context &ctx,
+		CompactTileSheet const&ts,
+		bool loadDefaultPalette) noexcept {
+	for (size_t i = 0; i < ts.pixels.size(); i += 2) {
+		uint16_t v = ts.pixels[i];
+		v |= static_cast<uint16_t>(ts.pixels[i + 1] << 8);
+		MEM_SPRITE_TILES[i] = v;
+	}
+	if (loadDefaultPalette && ts.defaultPalette) {
+		oxReturnError(loadSpritePalette(ctx, ts.defaultPalette));
+	}
+	setSpritesBpp(static_cast<unsigned>(ts.bpp));
+	return {};
+}
+
 ox::Error loadSpriteTileSheet(
 		Context &ctx,
 		ox::FileAddress const&tilesheetAddr,
 		bool loadDefaultPalette) noexcept {
-	auto &rom = ctx.rom();
-	oxRequire(tsStat, rom.stat(tilesheetAddr));
-	oxRequire(ts, rom.directAccess(tilesheetAddr));
-	unsigned bpp{};
-	GbaTileMapTarget target{
-		.bpp = bpp,
-		.defaultPalette = {},
-		.tileMap = MEM_SPRITE_TILES,
-	};
-	oxReturnError(ox::readMC({ts, static_cast<std::size_t>(tsStat.size)}, target));
-	if (loadDefaultPalette && target.defaultPalette) {
-		oxReturnError(loadSpritePalette(ctx, target.defaultPalette));
-	}
-	setSpritesBpp(bpp);
-	return {};
+	oxRequire(ts, keel::readObj<CompactTileSheet>(keelCtx(ctx), tilesheetAddr));
+	return loadSpriteTileSheet(ctx, *ts, loadDefaultPalette);
 }
 
 ox::Error loadSpriteTileSheet(
diff --git a/src/nostalgia/modules/core/src/opengl/gfx.cpp b/src/nostalgia/modules/core/src/opengl/gfx.cpp
index 19f77a4..e5dee25 100644
--- a/src/nostalgia/modules/core/src/opengl/gfx.cpp
+++ b/src/nostalgia/modules/core/src/opengl/gfx.cpp
@@ -572,20 +572,28 @@ static ox::Result<TileSheetData> buildSetTsd(
 	return setTsd;
 }
 
+ox::Error loadBgTileSheet(
+		Context &ctx,
+		uint_t cbb,
+		CompactTileSheet const&ts,
+		ox::Optional<unsigned> const&paletteBank) noexcept {
+	oxRequire(tsd, normalizeTileSheet(ts));
+	oxTracef("nostalgia.core.gfx.gl", "loadBgTexture: { cbbIdx: {}, w: {}, h: {} }", cbb, tsd.width, tsd.height);
+	ctx.cbbs[cbb].tex = renderer::createTexture(tsd.width, tsd.height, tsd.pixels.data());
+	if (paletteBank.has_value() && ts.defaultPalette) {
+		oxReturnError(loadBgPalette(ctx, *paletteBank, ts.defaultPalette));
+	}
+	return {};
+}
+
 ox::Error loadBgTileSheet(
 		Context &ctx,
 		uint_t cbb,
 		ox::FileAddress const&tilesheetAddr,
 		ox::Optional<unsigned> const&paletteBank) noexcept {
 	auto &kctx = keelCtx(ctx.turbineCtx);
-	oxRequire(tilesheet, readObj<CompactTileSheet>(kctx, tilesheetAddr));
-	oxRequire(tsd, normalizeTileSheet(*tilesheet));
-	oxTracef("nostalgia.core.gfx.gl", "loadBgTexture: { cbbIdx: {}, w: {}, h: {} }", cbb, tsd.width, tsd.height);
-	ctx.cbbs[cbb].tex = renderer::createTexture(tsd.width, tsd.height, tsd.pixels.data());
-	if (paletteBank.has_value() && tilesheet->defaultPalette) {
-		oxReturnError(loadBgPalette(ctx, *paletteBank, tilesheet->defaultPalette));
-	}
-	return {};
+	oxRequire(ts, readObj<CompactTileSheet>(kctx, tilesheetAddr));
+	return loadBgTileSheet(ctx, cbb, *ts, paletteBank);
 }
 
 ox::Error loadBgTileSheet(
@@ -599,19 +607,26 @@ ox::Error loadBgTileSheet(
 
 ox::Error loadSpriteTileSheet(
 		Context &ctx,
-		ox::FileAddress const&tilesheetAddr,
+		CompactTileSheet const&ts,
 		bool loadDefaultPalette) noexcept {
-	auto &kctx = keelCtx(ctx.turbineCtx);
-	oxRequire(tilesheet, readObj<CompactTileSheet>(kctx, tilesheetAddr));
-	oxRequire(tsd, normalizeTileSheet(*tilesheet));
+	oxRequire(tsd, normalizeTileSheet(ts));
 	oxTracef("nostalgia.core.gfx.gl", "loadSpriteTexture: { w: {}, h: {} }", tsd.width, tsd.height);
 	ctx.spriteBlocks.tex = renderer::createTexture(tsd.width, tsd.height, tsd.pixels.data());
 	if (loadDefaultPalette) {
-		oxReturnError(loadSpritePalette(ctx, tilesheet->defaultPalette));
+		oxReturnError(loadSpritePalette(ctx, ts.defaultPalette));
 	}
 	return {};
 }
 
+ox::Error loadSpriteTileSheet(
+		Context &ctx,
+		ox::FileAddress const&tilesheetAddr,
+		bool loadDefaultPalette) noexcept {
+	auto &kctx = keelCtx(ctx.turbineCtx);
+	oxRequire(ts, readObj<CompactTileSheet>(kctx, tilesheetAddr));
+	return loadSpriteTileSheet(ctx, *ts, loadDefaultPalette);
+}
+
 ox::Error loadSpriteTileSheet(
 		Context &ctx,
 		TileSheetSet const&set) noexcept {
diff --git a/src/nostalgia/modules/core/src/studio/tilesheeteditor/tilesheeteditor-imgui.cpp b/src/nostalgia/modules/core/src/studio/tilesheeteditor/tilesheeteditor-imgui.cpp
index da406f0..f14c445 100644
--- a/src/nostalgia/modules/core/src/studio/tilesheeteditor/tilesheeteditor-imgui.cpp
+++ b/src/nostalgia/modules/core/src/studio/tilesheeteditor/tilesheeteditor-imgui.cpp
@@ -15,16 +15,6 @@ namespace nostalgia::core {
 
 namespace ig = studio::ig;
 
-static ox::String configName(ox::StringView str) noexcept {
-	auto out = ox::String{str};
-	for (auto &c : out) {
-		if (c == '/' || c == '\\') {
-			c = '%';
-		}
-	}
-	return out;
-}
-
 struct TileSheetEditorConfig {
 	static constexpr auto TypeName = "net.drinkingtea.nostalgia.core.studio.TileSheetEditorConfig";
 	static constexpr auto TypeVersion = 1;
@@ -35,16 +25,6 @@ oxModelBegin(TileSheetEditorConfig)
 	oxModelFieldRename(activeSubsheet, active_subsheet)
 oxModelEnd()
 
-struct TileSheetEditorConfigs {
-	static constexpr auto TypeName = "net.drinkingtea.nostalgia.core.studio.TileSheetEditorConfigs";
-	static constexpr auto TypeVersion = 1;
-	ox::HashMap<ox::String, TileSheetEditorConfig> configs;
-};
-
-oxModelBegin(TileSheetEditorConfigs)
-	oxModelField(configs)
-oxModelEnd()
-
 static ox::Vector<uint32_t> normalizePixelSizes(
 		ox::Vector<uint8_t> const&inPixels,
 		int const bpp) noexcept {
@@ -120,7 +100,7 @@ TileSheetEditorImGui::TileSheetEditorImGui(studio::StudioContext &sctx, ox::Stri
 	m_model.paletteChanged.connect(this, &TileSheetEditorImGui::setPaletteSelection);
 	// load config
 	auto const&config = studio::readConfig<TileSheetEditorConfig>(
-			keelCtx(m_sctx), configName(itemPath()));
+			keelCtx(m_sctx), itemPath());
 	if (config.ok()) {
 		m_model.setActiveSubsheet(validateSubSheetIdx(m_model.img(), config.value.activeSubsheet));
 	}
@@ -537,9 +517,9 @@ ox::Error TileSheetEditorImGui::setPaletteSelection() noexcept {
 
 void TileSheetEditorImGui::setActiveSubsheet(TileSheet::SubSheetIdx path) noexcept {
 	m_model.setActiveSubsheet(path);
-	studio::editConfig<TileSheetEditorConfig>(keelCtx(m_sctx), configName(itemPath()),
-		[&path](TileSheetEditorConfig *config) {
-			config->activeSubsheet = std::move(path);
+	studio::editConfig<TileSheetEditorConfig>(keelCtx(m_sctx), itemPath(),
+		[&path](TileSheetEditorConfig &config) {
+			config.activeSubsheet = std::move(path);
 		});
 }
 
diff --git a/src/nostalgia/modules/core/src/tilesheet.cpp b/src/nostalgia/modules/core/src/tilesheet.cpp
index 18b62d0..fb336f7 100644
--- a/src/nostalgia/modules/core/src/tilesheet.cpp
+++ b/src/nostalgia/modules/core/src/tilesheet.cpp
@@ -52,7 +52,7 @@ TileSheet::SubSheet const *getSubsheet(TileSheet const&ts, SubSheetId const id)
 static ox::Optional<size_t> getPixelIdx(
 		TileSheet::SubSheet const&ss,
 		SubSheetId const id,
-		size_t idx,
+		size_t &idx,
 		int8_t const bpp) noexcept {
 	for (auto const&child: ss.subsheets) {
 		if (child.id == id) {
@@ -63,11 +63,12 @@ static ox::Optional<size_t> getPixelIdx(
 		}
 		idx += pixelCnt(child, bpp);
 	}
-	return {};
+	return ox::Optional<size_t>{};
 }
 
 size_t getTileIdx(TileSheet const&ts, SubSheetId const id) noexcept {
-	auto const out = getPixelIdx(ts.subsheet, id, 0, ts.bpp);
+	size_t idx{};
+	auto const out = getPixelIdx(ts.subsheet, id, idx, ts.bpp);
 	return out.or_value(0) / PixelsPerTile;
 }
 
diff --git a/src/olympic/keel/include/keel/assetmanager.hpp b/src/olympic/keel/include/keel/assetmanager.hpp
index 99f8d6b..b17d2cf 100644
--- a/src/olympic/keel/include/keel/assetmanager.hpp
+++ b/src/olympic/keel/include/keel/assetmanager.hpp
@@ -21,6 +21,17 @@ class AssetManager;
 template<typename T>
 class AssetRef;
 
+
+[[nodiscard]]
+constexpr bool valid(auto const&) noexcept {
+	return true;
+}
+
+[[nodiscard]]
+constexpr ox::Error repair(auto const&) noexcept {
+	return {};
+}
+
 #ifndef OX_BARE_METAL
 template<typename T>
 class AssetContainer {
@@ -215,6 +226,9 @@ class AssetManager {
 				ox::Result<AssetRef<T>> loadAsset(ox::StringView const assetId) noexcept {
 					auto &p = m_cache[assetId];
 					oxRequireM(obj, m_loader(assetId));
+					if (!valid(obj) && repair(obj)) {
+						return OxError(1, "asset is invalid state and could not be repaired");
+					}
 					if (!p) {
 						p = ox::make_unique<AssetContainer<T>>(std::move(obj));
 					} else {
diff --git a/src/olympic/studio/applib/src/studioapp.cpp b/src/olympic/studio/applib/src/studioapp.cpp
index dc74dd4..607627a 100644
--- a/src/olympic/studio/applib/src/studioapp.cpp
+++ b/src/olympic/studio/applib/src/studioapp.cpp
@@ -200,8 +200,8 @@ void StudioUI::drawTabs() noexcept {
 		if (ImGui::BeginTabItem(e->itemDisplayName().c_str(), &open, flags)) {
 			if (m_activeEditor != e.get()) {
 				m_activeEditor = e.get();
-				studio::editConfig<StudioConfig>(keelCtx(m_ctx), [&](StudioConfig *config) {
-					config->activeTabItemName = m_activeEditor->itemPath();
+				studio::editConfig<StudioConfig>(keelCtx(m_ctx), [&](StudioConfig &config) {
+					config.activeTabItemName = m_activeEditor->itemPath();
 				});
 			}
 			if (m_activeEditorUpdatePending == e.get()) {
@@ -255,8 +255,8 @@ void StudioUI::loadModules() noexcept {
 
 void StudioUI::toggleProjectExplorer() noexcept {
 	m_showProjectExplorer = !m_showProjectExplorer;
-	studio::editConfig<StudioConfig>(keelCtx(m_ctx), [&](StudioConfig *config) {
-		config->showProjectExplorer = m_showProjectExplorer;
+	studio::editConfig<StudioConfig>(keelCtx(m_ctx), [&](StudioConfig &config) {
+		config.showProjectExplorer = m_showProjectExplorer;
 	});
 }
 
@@ -339,9 +339,9 @@ ox::Error StudioUI::openProjectPath(ox::CRStringView path) noexcept {
 	m_project->fileDeleted.connect(&m_projectExplorer, &ProjectExplorer::refreshProjectTreeModel);
 	m_openFiles.clear();
 	m_editors.clear();
-	studio::editConfig<StudioConfig>(keelCtx(m_ctx), [&](StudioConfig *config) {
-		config->projectPath = ox::String(m_project->projectPath());
-		config->openFiles.clear();
+	studio::editConfig<StudioConfig>(keelCtx(m_ctx), [&](StudioConfig &config) {
+		config.projectPath = ox::String(m_project->projectPath());
+		config.openFiles.clear();
 	});
 	return m_projectExplorer.refreshProjectTreeModel();
 }
@@ -392,9 +392,9 @@ ox::Error StudioUI::openFileActiveTab(ox::CRStringView path, bool makeActiveTab)
 		m_activeEditorUpdatePending = editor;
 	}
 	// save to config
-	studio::editConfig<StudioConfig>(keelCtx(m_ctx), [&](StudioConfig *config) {
-		if (!config->openFiles.contains(path)) {
-			config->openFiles.emplace_back(path);
+	studio::editConfig<StudioConfig>(keelCtx(m_ctx), [&](StudioConfig &config) {
+		if (!config.openFiles.contains(path)) {
+			config.openFiles.emplace_back(path);
 		}
 	});
 	return {};
@@ -406,8 +406,8 @@ ox::Error StudioUI::closeFile(ox::CRStringView path) noexcept {
 	}
 	std::ignore = m_openFiles.erase(std::remove(m_openFiles.begin(), m_openFiles.end(), path));
 	// save to config
-	studio::editConfig<StudioConfig>(keelCtx(m_ctx), [&](StudioConfig *config) {
-			std::ignore = config->openFiles.erase(std::remove(config->openFiles.begin(), config->openFiles.end(), path));
+	studio::editConfig<StudioConfig>(keelCtx(m_ctx), [&](StudioConfig &config) {
+		std::ignore = config.openFiles.erase(std::remove(config.openFiles.begin(), config.openFiles.end(), path));
 	});
 	return {};
 }
diff --git a/src/olympic/studio/modlib/include/studio/configio.hpp b/src/olympic/studio/modlib/include/studio/configio.hpp
index 14d476e..69b4443 100644
--- a/src/olympic/studio/modlib/include/studio/configio.hpp
+++ b/src/olympic/studio/modlib/include/studio/configio.hpp
@@ -17,17 +17,29 @@
 
 namespace studio {
 
+namespace detail {
+inline ox::String slashesToPct(ox::StringView str) noexcept {
+	auto out = ox::String{str};
+	for (auto&c: out) {
+		if (c == '/' || c == '\\') {
+			c = '%';
+		}
+	}
+	return out;
+}
+}
+
 [[nodiscard]]
 ox::String configPath(keel::Context const&ctx) noexcept;
 
 template<typename T>
 ox::Result<T> readConfig(keel::Context &ctx, ox::CRStringView name) noexcept {
 	oxAssert(name != "", "Config type has no TypeName");
-	auto const path = ox::sfmt("/{}.json", name);
+	auto const path = ox::sfmt("/{}.json", detail::slashesToPct(name));
 	ox::PassThroughFS fs(configPath(ctx));
 	auto const [buff, err] = fs.read(path);
 	if (err) {
-		oxErrf("Could not read config file: {}\n", toStr(err));
+		//oxErrf("Could not read config file: {} - {}\n", path, toStr(err));
 		return err;
 	}
 	return ox::readOC<T>(buff);
@@ -40,25 +52,25 @@ ox::Result<T> readConfig(keel::Context &ctx) noexcept {
 }
 
 template<typename T>
-ox::Error writeConfig(keel::Context &ctx, ox::CRStringView name, T *data) noexcept {
+ox::Error writeConfig(keel::Context &ctx, ox::CRStringView name, T const&data) noexcept {
 	oxAssert(name != "", "Config type has no TypeName");
-	auto const path = ox::sfmt("/{}.json", name);
+	auto const path = ox::sfmt("/{}.json", detail::slashesToPct(name));
 	ox::PassThroughFS fs(configPath(ctx));
 	if (auto const err = fs.mkdir("/", true)) {
-		oxErrf("Could not create config directory: {}\n", toStr(err));
+		//oxErrf("Could not create config directory: {} - {}\n", path, toStr(err));
 		return err;
 	}
-	oxRequireM(buff, ox::writeOC(*data));
+	oxRequireM(buff, ox::writeOC(data));
 	*buff.back().value = '\n';
 	if (auto const err = fs.write(path, buff.data(), buff.size())) {
-		oxErrf("Could not read config file: {}\n", toStr(err));
+		//oxErrf("Could not read config file: {} - {}\n", path, toStr(err));
 		return OxError(2, "Could not read config file");
 	}
 	return {};
 }
 
 template<typename T>
-ox::Error writeConfig(keel::Context &ctx, T *data) noexcept {
+ox::Error writeConfig(keel::Context &ctx, T const&data) noexcept {
 	constexpr auto TypeName = ox::requireModelTypeName<T>();
 	return writeConfig(ctx, TypeName, data);
 }
@@ -68,7 +80,7 @@ void openConfig(keel::Context &ctx, ox::CRStringView name, Func f) noexcept {
 	oxAssert(name != "", "Config type has no TypeName");
 	auto const [c, err] = readConfig<T>(ctx, name);
 	oxLogError(err);
-	f(&c);
+	f(c);
 }
 
 template<typename T, typename Func>
@@ -82,8 +94,8 @@ void editConfig(keel::Context &ctx, ox::CRStringView name, Func f) noexcept {
 	oxAssert(name !=  "", "Config type has no TypeName");
 	auto [c, err] = readConfig<T>(ctx, name);
 	oxLogError(err);
-	f(&c);
-	oxLogError(writeConfig(ctx, name, &c));
+	f(c);
+	oxLogError(writeConfig(ctx, name, c));
 }
 
 template<typename T, typename Func>
diff --git a/src/olympic/studio/modlib/src/task.cpp b/src/olympic/studio/modlib/src/task.cpp
index b966ee3..9aa202a 100644
--- a/src/olympic/studio/modlib/src/task.cpp
+++ b/src/olympic/studio/modlib/src/task.cpp
@@ -10,6 +10,7 @@ namespace studio {
 
 void TaskRunner::update(turbine::Context &ctx) noexcept {
 	std::ignore = m_tasks.erase(std::remove_if(m_tasks.begin(), m_tasks.end(), [&](ox::UPtr<studio::Task> &t) {
+		if (!t) { return true; }
 		auto const done = t->update(ctx) == TaskState::Done;
 		if (done) {
 			t->finished.emit();
diff --git a/src/olympic/turbine/include/turbine/turbine.hpp b/src/olympic/turbine/include/turbine/turbine.hpp
index f12b18e..d24897b 100644
--- a/src/olympic/turbine/include/turbine/turbine.hpp
+++ b/src/olympic/turbine/include/turbine/turbine.hpp
@@ -14,6 +14,8 @@
 
 namespace turbine {
 
+using TimeMs = uint64_t;
+
 ox::Result<ContextUPtr> init(ox::UPtr<ox::FileSystem> &&fs, ox::CRStringView appName) noexcept;
 
 ox::Error run(Context &ctx) noexcept;
@@ -21,7 +23,7 @@ ox::Error run(Context &ctx) noexcept;
 // Returns the number of milliseconds that have passed since the start of the
 // program.
 [[nodiscard]]
-uint64_t ticksMs(Context const&ctx) noexcept;
+TimeMs ticksMs(Context const&ctx) noexcept;
 
 void requestShutdown(Context &ctx) noexcept;
 
diff --git a/src/olympic/turbine/src/gba/turbine.cpp b/src/olympic/turbine/src/gba/turbine.cpp
index aed5fb5..96432a2 100644
--- a/src/olympic/turbine/src/gba/turbine.cpp
+++ b/src/olympic/turbine/src/gba/turbine.cpp
@@ -8,6 +8,7 @@
 #include <keel/keel.hpp>
 #include <turbine/context.hpp>
 #include <turbine/gfx.hpp>
+#include <turbine/turbine.hpp>
 
 #include "context.hpp"
 #include "turbine.hpp"
@@ -71,7 +72,7 @@ ox::Result<ContextUPtr> init(
 void shutdown(Context&) noexcept {
 }
 
-uint64_t ticksMs(Context const&) noexcept {
+TimeMs ticksMs(Context const&) noexcept {
 	return g_timerMs;
 }
 
diff --git a/src/olympic/turbine/src/glfw/context.hpp b/src/olympic/turbine/src/glfw/context.hpp
index 6a6cd1d..522e3c1 100644
--- a/src/olympic/turbine/src/glfw/context.hpp
+++ b/src/olympic/turbine/src/glfw/context.hpp
@@ -8,12 +8,13 @@
 #include <turbine/context.hpp>
 #include <turbine/gfx.hpp>
 #include <turbine/event.hpp>
+#include <turbine/turbine.hpp>
 
 namespace turbine {
 
 class Context {
 	public:
-		UpdateHandler updateHandler = [](Context&) -> int {return 0;};
+		UpdateHandler updateHandler = [](Context&) -> int {return -1;};
 		keel::Context keelCtx;
 		KeyEventHandler keyEventHandler = nullptr;
 		ox::AnyPtr applicationData;
@@ -24,7 +25,7 @@ class Context {
 		struct GLFWwindow *window = nullptr;
 		int refreshWithinMs = 0;
 		ox::Vector<gl::Drawer*, 5> drawers;
-		int64_t startTime = 0;
+		TimeMs startTime = 0;
 		uint64_t wakeupTime = 0;
 		uint64_t keysDown = 0;
 		uint64_t prevFpsCheckTime = 0;
diff --git a/src/olympic/turbine/src/glfw/turbine.cpp b/src/olympic/turbine/src/glfw/turbine.cpp
index 2865423..fb307e6 100644
--- a/src/olympic/turbine/src/glfw/turbine.cpp
+++ b/src/olympic/turbine/src/glfw/turbine.cpp
@@ -45,7 +45,8 @@ ox::Result<ContextUPtr> init(
 	auto ctx = ox::make_unique<Context>();
 	oxReturnError(keel::init(ctx->keelCtx, std::move(fs), appName));
 	using namespace std::chrono;
-	ctx->startTime = duration_cast<milliseconds>(system_clock::now().time_since_epoch()).count();
+	ctx->startTime = static_cast<TimeMs>(
+			duration_cast<milliseconds>(system_clock::now().time_since_epoch()).count());
 	glfwInit();
 	oxReturnError(initGfx(*ctx));
 	glfwSetWindowSizeCallback(ctx->window, draw);
@@ -67,24 +68,26 @@ static void tickFps(Context &ctx, uint64_t nowMs) noexcept {
 }
 
 ox::Error run(Context &ctx) noexcept {
-	int sleepTime = 0;
+	uint64_t sleepTime = 0;
 	while (!glfwWindowShouldClose(ctx.window)) {
 		ctx.refreshWithinMs = 10 * 1000; // refresh within 10 seconds
 		glfwPollEvents();
 		auto const ticks = ticksMs(ctx);
 		if (ctx.wakeupTime <= ticks) {
-			 sleepTime = ctx.updateHandler(ctx);
-			 if (sleepTime >= 0) {
-				  ctx.wakeupTime = ticks + static_cast<unsigned>(sleepTime);
+			 auto const st = ctx.updateHandler(ctx);
+			 if (st >= 0) {
+				  ctx.wakeupTime = ticks + static_cast<unsigned>(st);
+				  sleepTime = static_cast<uint64_t>(st);
 			 } else {
 				  ctx.wakeupTime = ~uint64_t(0);
+				  sleepTime = ctx.wakeupTime - ticks;
 			 }
 		} else {
-			sleepTime = static_cast<int>(ctx.wakeupTime - ticks);
+			sleepTime = ctx.wakeupTime - ticks;
 		}
 		tickFps(ctx, ticks);
 		draw(ctx);
-		auto const realSleepTime = ox::min(ctx.refreshWithinMs, sleepTime);
+		auto const realSleepTime = ox::min(static_cast<uint64_t>(ctx.refreshWithinMs), sleepTime);
 		if (realSleepTime) {
 			if (ctx.uninterruptedRefreshes) {
 				--ctx.uninterruptedRefreshes;
@@ -108,10 +111,10 @@ void shutdown(Context &ctx) noexcept {
 	}
 }
 
-uint64_t ticksMs(Context const&ctx) noexcept {
+TimeMs ticksMs(Context const&ctx) noexcept {
 	using namespace std::chrono;
 	auto const now = duration_cast<milliseconds>(system_clock::now().time_since_epoch()).count();
-	return static_cast<uint64_t>(now - ctx.startTime);
+	return static_cast<TimeMs>(now) - ctx.startTime;
 }
 
 bool buttonDown(Context const&ctx, Key key) noexcept {