diff --git a/src/nostalgia/modules/core/include/nostalgia/core/tilesheet.hpp b/src/nostalgia/modules/core/include/nostalgia/core/tilesheet.hpp
index 1eaa080..cf7998c 100644
--- a/src/nostalgia/modules/core/include/nostalgia/core/tilesheet.hpp
+++ b/src/nostalgia/modules/core/include/nostalgia/core/tilesheet.hpp
@@ -238,7 +238,7 @@ ox::Error resizeSubsheet(TileSheet::SubSheet &ss, int8_t pBpp, ox::Size const&sz
  * @return a valid version of idx
  */
 [[nodiscard]]
-TileSheet::SubSheetIdx validateSubSheetIdx(TileSheet const&ts, TileSheet::SubSheetIdx const&idx) noexcept;
+TileSheet::SubSheetIdx validateSubSheetIdx(TileSheet const&ts, TileSheet::SubSheetIdx idx) noexcept;
 
 [[nodiscard]]
 TileSheet::SubSheet const&getSubSheet(
diff --git a/src/nostalgia/modules/core/src/studio/tilesheeteditor/commands/addsubsheetcommand.cpp b/src/nostalgia/modules/core/src/studio/tilesheeteditor/commands/addsubsheetcommand.cpp
index a822cc7..8aa99f1 100644
--- a/src/nostalgia/modules/core/src/studio/tilesheeteditor/commands/addsubsheetcommand.cpp
+++ b/src/nostalgia/modules/core/src/studio/tilesheeteditor/commands/addsubsheetcommand.cpp
@@ -46,9 +46,11 @@ ox::Error AddSubSheetCommand::undo() noexcept {
 		parent.columns = s.columns;
 		parent.pixels = std::move(s.pixels);
 		parent.subsheets.clear();
+		--m_img.idIt;
 	} else {
 		for (auto idx = m_addedSheets.rbegin(); idx != m_addedSheets.rend(); ++idx) {
 			oxReturnError(rmSubSheet(m_img, *idx));
+			--m_img.idIt;
 		}
 	}
 	return {};
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 c5d16c1..da406f0 100644
--- a/src/nostalgia/modules/core/src/studio/tilesheeteditor/tilesheeteditor-imgui.cpp
+++ b/src/nostalgia/modules/core/src/studio/tilesheeteditor/tilesheeteditor-imgui.cpp
@@ -212,8 +212,8 @@ void TileSheetEditorImGui::draw(studio::StudioContext&) noexcept {
 		}
 	}
 	auto const paneSize = ImGui::GetContentRegionAvail();
-	auto const tileSheetParentSize = ImVec2(paneSize.x - m_palViewWidth, paneSize.y);
-	auto const fbSize = ox::Vec2(tileSheetParentSize.x - 16, tileSheetParentSize.y - 16);
+	auto const tileSheetParentSize = ImVec2{paneSize.x - m_palViewWidth, paneSize.y};
+	auto const fbSize = ox::Vec2{tileSheetParentSize.x - 16, tileSheetParentSize.y - 16};
 	ImGui::BeginChild("TileSheetView", tileSheetParentSize, true);
 	{
 		drawTileSheet(fbSize);
@@ -225,7 +225,7 @@ void TileSheetEditorImGui::draw(studio::StudioContext&) noexcept {
 		auto const controlsSize = ImGui::GetContentRegionAvail();
 		ImGui::BeginChild("ToolBox", {m_palViewWidth - 24, 30}, true);
 		{
-			auto const btnSz = ImVec2(45, 14);
+			auto const btnSz = ImVec2{45, 14};
 			if (ImGui::Selectable("Select", m_tool == TileSheetTool::Select, 0, btnSz)) {
 				m_tool = TileSheetTool::Select;
 			}
@@ -388,7 +388,7 @@ ox::Error TileSheetEditorImGui::exportSubhseetToPng(int scale) noexcept {
 
 void TileSheetEditorImGui::drawTileSheet(ox::Vec2 const&fbSize) noexcept {
 	auto const winPos = ImGui::GetWindowPos();
-	auto const fbSizei = ox::Size(static_cast<int>(fbSize.x), static_cast<int>(fbSize.y));
+	auto const fbSizei = ox::Size{static_cast<int>(fbSize.x), static_cast<int>(fbSize.y)};
 	if (m_framebuffer.width != fbSizei.width || m_framebuffer.height != fbSizei.height) {
 		glutils::resizeInitFrameBuffer(m_framebuffer, fbSizei.width, fbSizei.height);
 		m_view.resizeView(fbSize);
@@ -404,11 +404,11 @@ void TileSheetEditorImGui::drawTileSheet(ox::Vec2 const&fbSize) noexcept {
 	ImGui::Image(
 		ig::toImTextureID(m_framebuffer.color.id),
 		static_cast<ImVec2>(fbSize),
-		ImVec2(0, 1),
-		ImVec2(1, 0));
+		{0, 1},
+		{1, 0});
 	// handle input, this must come after drawing
 	auto const&io = ImGui::GetIO();
-	auto const mousePos = ox::Vec2(ImGui::GetMousePos());
+	auto const mousePos = ox::Vec2{ImGui::GetMousePos()};
 	if (ImGui::IsItemHovered()) {
 		auto const wheel = io.MouseWheel;
 		auto const wheelh = io.MouseWheelH;
@@ -436,7 +436,7 @@ void TileSheetEditorImGui::drawTileSheet(ox::Vec2 const&fbSize) noexcept {
 		}
 	}
 	if (ImGui::BeginPopupContextItem("TileMenu", ImGuiPopupFlags_MouseButtonRight)) {
-		auto const popupPos = ox::Vec2(ImGui::GetWindowPos());
+		auto const popupPos = ox::Vec2{ImGui::GetWindowPos()};
 		if (ImGui::MenuItem("Insert Tile")) {
 			m_view.insertTile(fbSize, clickPos(winPos, popupPos));
 		}
@@ -504,8 +504,8 @@ void TileSheetEditorImGui::drawPaletteSelector() noexcept {
 					auto ic = ImGui::GetColorU32(ImVec4(redf(c), greenf(c), bluef(c), 1));
 					ImGui::TableSetBgColor(ImGuiTableBgTarget_CellBg, ic);
 					ImGui::TableNextColumn();
-					auto const&name = pal.colorInfo[i].name;
-					ImGui::Text("%s", name.c_str());
+					auto const&name =  i < pal.colorInfo.size() ? pal.colorInfo[i].name.c_str() : "";
+					ImGui::Text("%s", name);
 					ImGui::TableNextColumn();
 					ImGui::Text("(%02d, %02d, %02d)", red16(c), green16(c), blue16(c));
 					ImGui::TableNextRow();
@@ -556,7 +556,7 @@ void TileSheetEditorImGui::SubSheetEditor::draw(turbine::Context &tctx) noexcept
 	auto const modSize = m_cols > 0;
 	auto constexpr popupWidth = 235.f;
 	auto const popupHeight = modSize ? 130.f : 85.f;
-	auto const popupSz = ImVec2(popupWidth, popupHeight);
+	auto const popupSz = ImVec2{popupWidth, popupHeight};
 	if (ig::BeginPopup(tctx, popupName, m_show, popupSz)) {
 		ImGui::InputText("Name", m_name.data(), m_name.cap());
 		if (modSize) {
@@ -581,7 +581,7 @@ void TileSheetEditorImGui::ExportMenu::draw(turbine::Context &tctx) noexcept {
 	}
 	constexpr auto popupWidth = 235.f;
 	constexpr auto popupHeight = 85.f;
-	constexpr auto popupSz = ImVec2(popupWidth, popupHeight);
+	constexpr auto popupSz = ImVec2{popupWidth, popupHeight};
 	if (ig::BeginPopup(tctx, popupName, m_show, popupSz)) {
 		ImGui::InputInt("Scale", &m_scale);
 		m_scale = ox::clamp(m_scale, 1, 50);
diff --git a/src/nostalgia/modules/core/src/tilesheet.cpp b/src/nostalgia/modules/core/src/tilesheet.cpp
index 9f622ad..18b62d0 100644
--- a/src/nostalgia/modules/core/src/tilesheet.cpp
+++ b/src/nostalgia/modules/core/src/tilesheet.cpp
@@ -191,27 +191,28 @@ ox::Result<ox::StringView> getNameFor(TileSheet::SubSheet const&ss, SubSheetId p
 
 
 TileSheet::SubSheetIdx validateSubSheetIdx(
-		TileSheet::SubSheetIdx const&pIdx,
+		TileSheet::SubSheetIdx &&pIdx,
 		std::size_t pIdxIt,
 		TileSheet::SubSheet const&pSubsheet) noexcept {
-	if (pIdxIt == pIdx.size()) {
-		return pIdx;
+	if (pIdxIt >= pIdx.size()) {
+		return std::move(pIdx);
 	}
-	const auto currentIdx = pIdx[pIdxIt];
+	auto &currentIdx = pIdx[pIdxIt];
 	if (pSubsheet.subsheets.size() <= currentIdx) {
-		auto out = pIdx;
-		if (!pSubsheet.subsheets.empty()) {
-			*out.back().value = pSubsheet.subsheets.size() - 1;
+		if (pSubsheet.subsheets.empty()) {
+			// currentIdx could not be repaired, remove
+			// this and all succeeding idxs and return
+			pIdx.resize(pIdxIt);
+			return std::move(pIdx);
 		} else {
-			out.pop_back();
+			currentIdx = pSubsheet.subsheets.size() - 1;
 		}
-		return out;
 	}
-	return validateSubSheetIdx(pIdx, pIdxIt + 1, pSubsheet.subsheets[pIdx[pIdxIt]]);
+	return validateSubSheetIdx(std::move(pIdx), pIdxIt + 1, pSubsheet.subsheets[currentIdx]);
 }
 
-TileSheet::SubSheetIdx validateSubSheetIdx(TileSheet const&ts, TileSheet::SubSheetIdx const&idx) noexcept {
-	return validateSubSheetIdx(idx, 0, ts.subsheet);
+TileSheet::SubSheetIdx validateSubSheetIdx(TileSheet const&ts, TileSheet::SubSheetIdx idx) noexcept {
+	return validateSubSheetIdx(std::move(idx), 0, ts.subsheet);
 }
 
 const TileSheet::SubSheet &getSubSheet(
diff --git a/src/olympic/keel/include/keel/assetmanager.hpp b/src/olympic/keel/include/keel/assetmanager.hpp
index 3daefc6..99f8d6b 100644
--- a/src/olympic/keel/include/keel/assetmanager.hpp
+++ b/src/olympic/keel/include/keel/assetmanager.hpp
@@ -302,7 +302,7 @@ class AssetManager {
 template<typename T>
 class AssetRef {
 	private:
-		T const*const m_obj = nullptr;
+		T const* m_obj = nullptr;
 
 	public:
 		constexpr AssetRef() noexcept = default;
diff --git a/src/olympic/studio/applib/src/main.cpp b/src/olympic/studio/applib/src/main.cpp
index b38ec36..324cebc 100644
--- a/src/olympic/studio/applib/src/main.cpp
+++ b/src/olympic/studio/applib/src/main.cpp
@@ -28,12 +28,6 @@ class StudioUIDrawer: public turbine::gl::Drawer {
 		}
 };
 
-static int updateHandler(turbine::Context &ctx) noexcept {
-	auto sctx = turbine::applicationData<studio::StudioContext>(ctx);
-	sctx->ui.update();
-	return 16;
-}
-
 static void keyEventHandler(turbine::Context &ctx, turbine::Key key, bool down) noexcept {
 	auto sctx = turbine::applicationData<studio::StudioContext>(ctx);
 	sctx->ui.handleKeyEvent(key, down);
@@ -45,9 +39,8 @@ static ox::Error runApp(
 		ox::UPtr<ox::FileSystem> &&fs) noexcept {
 	oxRequireM(ctx, turbine::init(std::move(fs), appName));
 	turbine::setWindowTitle(*ctx, keelCtx(*ctx).appName);
-	turbine::setUpdateHandler(*ctx, updateHandler);
 	turbine::setKeyEventHandler(*ctx, keyEventHandler);
-	turbine::setConstantRefresh(*ctx, false);
+	turbine::setRefreshWithin(*ctx, 0);
 	StudioUI ui(*ctx, projectDataDir);
 	StudioUIDrawer drawer(ui);
 	turbine::gl::addDrawer(*ctx, &drawer);
@@ -68,7 +61,7 @@ static ox::Error run(
 		static_cast<uint64_t>(time << 1)
 	});
 	// run app
-	auto const err = runApp(appName, projectDataDir, ox::UPtr<ox::FileSystem>(nullptr));
+	auto const err = runApp(appName, projectDataDir, ox::UPtr<ox::FileSystem>{});
 	oxAssert(err, "Something went wrong...");
 	return err;
 }
diff --git a/src/olympic/studio/applib/src/studioapp.cpp b/src/olympic/studio/applib/src/studioapp.cpp
index 4fc9206..dc74dd4 100644
--- a/src/olympic/studio/applib/src/studioapp.cpp
+++ b/src/olympic/studio/applib/src/studioapp.cpp
@@ -78,10 +78,6 @@ StudioUI::StudioUI(turbine::Context &ctx, ox::StringView projectDataDir) noexcep
 	}
 }
 
-void StudioUI::update() noexcept {
-	m_taskRunner.update(m_ctx);
-}
-
 void StudioUI::handleKeyEvent(turbine::Key key, bool down) noexcept {
 	for (auto p : m_popups) {
 		if (p->isOpen()) {
@@ -124,6 +120,7 @@ void StudioUI::draw() noexcept {
 	}
 	ImGui::End();
 	handleKeyInput();
+	m_taskRunner.update(m_ctx);
 }
 
 void StudioUI::drawMenu() noexcept {
@@ -212,7 +209,6 @@ void StudioUI::drawTabs() noexcept {
 			}
 			if (m_activeEditorOnLastDraw != e.get()) [[unlikely]] {
 				m_activeEditor->onActivated();
-				turbine::setConstantRefresh(m_ctx, m_activeEditor->requiresConstantRefresh());
 			}
 			e->draw(m_sctx);
 			m_activeEditorOnLastDraw = e.get();
diff --git a/src/olympic/studio/applib/src/studioapp.hpp b/src/olympic/studio/applib/src/studioapp.hpp
index 5a32c7b..30ae799 100644
--- a/src/olympic/studio/applib/src/studioapp.hpp
+++ b/src/olympic/studio/applib/src/studioapp.hpp
@@ -50,8 +50,6 @@ class StudioUI: public ox::SignalHandler {
 	public:
 		explicit StudioUI(turbine::Context &ctx, ox::StringView projectDataDir) noexcept;
 
-		void update() noexcept;
-
 		void handleKeyEvent(turbine::Key, bool down) noexcept;
 
 		[[nodiscard]]
diff --git a/src/olympic/turbine/include/turbine/gfx.hpp b/src/olympic/turbine/include/turbine/gfx.hpp
index 0d2b135..7e863cb 100644
--- a/src/olympic/turbine/include/turbine/gfx.hpp
+++ b/src/olympic/turbine/include/turbine/gfx.hpp
@@ -43,6 +43,12 @@ ox::Bounds getWindowBounds(Context &ctx) noexcept;
 
 ox::Error setWindowBounds(Context &ctx, ox::Bounds const&bnds) noexcept;
 
-void setConstantRefresh(Context &ctx, bool r) noexcept;
+/**
+ * Tells Turbine to refresh the screen within the specified period of time.
+ * If the requested value is greater than the current value, the call has no effect.
+ * @param ctx - Context
+ * @param ms - milliseconds
+ */
+void setRefreshWithin(Context &ctx, int ms) noexcept;
 
 }
diff --git a/src/olympic/turbine/src/gba/turbine.cpp b/src/olympic/turbine/src/gba/turbine.cpp
index d67e9d4..aed5fb5 100644
--- a/src/olympic/turbine/src/gba/turbine.cpp
+++ b/src/olympic/turbine/src/gba/turbine.cpp
@@ -71,7 +71,7 @@ ox::Result<ContextUPtr> init(
 void shutdown(Context&) noexcept {
 }
 
-uint64_t ticksMs(Context&) noexcept {
+uint64_t 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 6a08a7d..6a6cd1d 100644
--- a/src/olympic/turbine/src/glfw/context.hpp
+++ b/src/olympic/turbine/src/glfw/context.hpp
@@ -22,8 +22,7 @@ class Context {
 		int uninterruptedRefreshes = 3;
 		ox::UPtr<BaseClipboardObject> clipboard;
 		struct GLFWwindow *window = nullptr;
-		// sets screen refresh to constant instead of only on event
-		bool constantRefresh = true;
+		int refreshWithinMs = 0;
 		ox::Vector<gl::Drawer*, 5> drawers;
 		int64_t startTime = 0;
 		uint64_t wakeupTime = 0;
diff --git a/src/olympic/turbine/src/glfw/gfx.cpp b/src/olympic/turbine/src/glfw/gfx.cpp
index e3883f2..9eeef90 100644
--- a/src/olympic/turbine/src/glfw/gfx.cpp
+++ b/src/olympic/turbine/src/glfw/gfx.cpp
@@ -260,8 +260,8 @@ ox::Error setWindowBounds(Context &ctx, ox::Bounds const&bnds) noexcept {
 	return {};
 }
 
-void setConstantRefresh(Context &ctx, bool r) noexcept {
-	ctx.constantRefresh = r;
+void setRefreshWithin(Context &ctx, int ms) noexcept {
+	ctx.refreshWithinMs = ox::min(ms, ctx.refreshWithinMs);
 }
 
 }
diff --git a/src/olympic/turbine/src/glfw/turbine.cpp b/src/olympic/turbine/src/glfw/turbine.cpp
index 7003e86..2865423 100644
--- a/src/olympic/turbine/src/glfw/turbine.cpp
+++ b/src/olympic/turbine/src/glfw/turbine.cpp
@@ -69,6 +69,7 @@ static void tickFps(Context &ctx, uint64_t nowMs) noexcept {
 ox::Error run(Context &ctx) noexcept {
 	int sleepTime = 0;
 	while (!glfwWindowShouldClose(ctx.window)) {
+		ctx.refreshWithinMs = 10 * 1000; // refresh within 10 seconds
 		glfwPollEvents();
 		auto const ticks = ticksMs(ctx);
 		if (ctx.wakeupTime <= ticks) {
@@ -79,15 +80,16 @@ ox::Error run(Context &ctx) noexcept {
 				  ctx.wakeupTime = ~uint64_t(0);
 			 }
 		} else {
-			sleepTime = 10;
+			sleepTime = static_cast<int>(ctx.wakeupTime - ticks);
 		}
 		tickFps(ctx, ticks);
 		draw(ctx);
-		if (!ctx.constantRefresh) {
+		auto const realSleepTime = ox::min(ctx.refreshWithinMs, sleepTime);
+		if (realSleepTime) {
 			if (ctx.uninterruptedRefreshes) {
 				--ctx.uninterruptedRefreshes;
 			} else {
-				glfwWaitEventsTimeout(sleepTime);
+				glfwWaitEventsTimeout(static_cast<double>(realSleepTime) / 1000);
 			}
 		}
 	}