diff --git a/Build/PTM.exe b/Build/PTM.exe
index 9493ad64..ead6df47 100644
Binary files a/Build/PTM.exe and b/Build/PTM.exe differ
diff --git a/Build/test.ptml b/Build/test.ptml
index f83e52fa..d63b329e 100644
--- a/Build/test.ptml
+++ b/Build/test.ptml
@@ -1,4 +1,5 @@
 O35bIFRFU1QgUFJPR1JBTSBdfn5+fn5+fn5+fn5+fn5+fn5+fn5+fn5+
+a2V5LmVzYy5vbg==
 Q0FMTCBpbml0X2Nocg==
 Q0FMTCBpbml0X3BhbA==
 
diff --git a/PTM/t_command.cpp b/PTM/t_command.cpp
index 5cbcc06d..80092ced 100644
--- a/PTM/t_command.cpp
+++ b/PTM/t_command.cpp
@@ -42,7 +42,8 @@ bool t_command::execute(string& cmd, t_params& args) {
 	else if (cmd == "TILE.STORE")	store_cur_tile(args);
 	else if (cmd == "TILE.PSTORE")	parse_and_store_tile(args);
 	else if (cmd == "TILE.LOAD")	load_cur_tile(args);
-	else if (cmd == "TILE.TRA")		set_tile_transparency(args);
+	else if (cmd == "TILE.TRA.ON")	set_tile_transparency(args, true);
+	else if (cmd == "TILE.TRA.OFF")	set_tile_transparency(args, false);
 	// Tile buffer cursor
 	else if (cmd == "CSR.LAYER")	select_layer(args);
 	else if (cmd == "CSR.SET")		set_cursor_pos(args);
@@ -72,6 +73,8 @@ bool t_command::execute(string& cmd, t_params& args) {
 	else if (cmd == "KEY.GET")		get_key_pressed(args);
 	else if (cmd == "KEY.CALL")		call_if_key_pressed(args);
 	else if (cmd == "KEY.GOTO")		goto_if_key_pressed(args);
+	else if (cmd == "KEY.ESC.ON")	allow_exit_on_escape_key(args, true);
+	else if (cmd == "KEY.ESC.OFF")	allow_exit_on_escape_key(args, false);
 	// Debug
 	else if (cmd == "DBG.FILE")		save_debug_file(args);
 	// Conditionals
@@ -398,10 +401,9 @@ void t_command::set_wnd_bgcolor(t_params& arg) {
 	ARGC(1);
 	machine->wnd->SetBackColor(machine->pal->GetColorRGB(intp->require_number(arg[0])));
 }
-void t_command::set_tile_transparency(t_params& arg) {
-	ARGC(1);
-	int value = intp->require_number(arg[0]);
-	machine->tile_transparency = value > 0;
+void t_command::set_tile_transparency(t_params& arg, bool transparent) {
+	ARGC(0);
+	machine->tile_transparency = transparent;
 }
 void t_command::select_layer(t_params& arg) {
 	ARGC(1);
@@ -727,3 +729,8 @@ void t_command::increment_variable(t_params& arg) {
 	auto& var = machine->vars[arr_id];
 	machine->vars[arr_id] = String::ToString(String::ToInt(var.value) + 1);
 }
+
+void t_command::allow_exit_on_escape_key(t_params& arg, bool allow) {
+	ARGC(0);
+	machine->exit_key = allow ? SDLK_ESCAPE : 0;
+}
diff --git a/PTM/t_command.h b/PTM/t_command.h
index 2a046ff3..8e38ee56 100644
--- a/PTM/t_command.h
+++ b/PTM/t_command.h
@@ -40,7 +40,7 @@ struct t_command {
 	void clear_layer(t_params& arg);
 	void clear_rect(t_params& arg);
 	void set_wnd_bgcolor(t_params& arg);
-	void set_tile_transparency(t_params& arg);
+	void set_tile_transparency(t_params& arg, bool transparent);
 	void select_layer(t_params& arg);
 	void define_char(t_params& arg);
 	void define_color(t_params& arg);
@@ -79,4 +79,5 @@ struct t_command {
 	void clear_array(t_params& arg);
 	void copy_array(t_params& arg);
 	void increment_variable(t_params& arg);
+	void allow_exit_on_escape_key(t_params& arg, bool allow);
 };
diff --git a/PTM/t_compiler.cpp b/PTM/t_compiler.cpp
index 368ba295..0b4ede8e 100644
--- a/PTM/t_compiler.cpp
+++ b/PTM/t_compiler.cpp
@@ -7,9 +7,9 @@ void t_compiler::run(t_program* prg) {
 	prg->lines.clear();
 	prg->labels.clear();
 	int src_line_nr = 1;
-	for (auto& srcline : prg->src_lines) {
+	for (auto& src_line : prg->src_lines) {
 		t_program_line new_line;
-		bool must_add_line = compile(prg, &new_line, srcline, src_line_nr);
+		bool must_add_line = compile(prg, &new_line, src_line, src_line_nr);
 		if (must_add_line) {
 			prg->lines.push_back(new_line);
 		}
@@ -17,14 +17,21 @@ void t_compiler::run(t_program* prg) {
 	}
 }
 bool t_compiler::compile(t_program* prg, t_program_line* new_line, string src_line, int src_line_nr) {
-	int line_ix = prg->lines.size();
+	if (String::StartsWith(src_line, ' ')) {
+		add_error(src_line_nr, src_line, "Leading whitespace is not allowed");
+		return false;
+	}
 	src_line = String::Trim(src_line);
 	if (String::StartsWith(src_line, ';')) {
 		return false;
 	}
 	if (String::StartsWith(src_line, ":")) {
 		string label = String::Trim(String::Skip(src_line, 1));
-		prg->labels[label] = line_ix;
+		prg->labels[label] = prg->lines.size();
+		return false;
+	}
+	if (!src_line.empty() && !String::StartsWithLetter(src_line)) {
+		add_error(src_line_nr, src_line, "Syntax error");
 		return false;
 	}
 	new_line->src = src_line;
@@ -118,6 +125,6 @@ bool t_compiler::compile(t_program* prg, t_program_line* new_line, string src_li
 	return true;
 }
 void t_compiler::add_error(int line, string src, string msg) {
-	errors.push_back(String::Format("At line %i:\n%s\n\n%s", 
+	errors.push_back(String::Format("COMPILATION ERROR\nAt line %i:\n%s\n\n%s", 
 		line, msg.c_str(), src.c_str()));
 }
diff --git a/PTM/t_interpreter.cpp b/PTM/t_interpreter.cpp
index 9d143ae5..5bf42d8a 100644
--- a/PTM/t_interpreter.cpp
+++ b/PTM/t_interpreter.cpp
@@ -71,6 +71,8 @@ void t_interpreter::execute_current_line() {
 void t_interpreter::on_keydown(SDL_Keycode key, bool ctrl, bool shift, bool alt) {
 	if (key == SDLK_RETURN && TKey::Alt()) {
 		wnd->ToggleFullscreen();
+	} else if (machine->exit_key != 0 && key == machine->exit_key) {
+		running = false;
 	} else {
 		machine->last_key_pressed = key;
 	}
@@ -78,7 +80,7 @@ void t_interpreter::on_keydown(SDL_Keycode key, bool ctrl, bool shift, bool alt)
 void t_interpreter::abort(string error) {
 	running = false;
 	if (cur_line) {
-		errors.push_back(String::Format("At line %i:\n%s\n\n%s",
+		errors.push_back(String::Format("RUNTIME ERROR\nAt line %i:\n%s\n\n%s",
 			cur_line->src_line_nr, error.c_str(), cur_line->src.c_str()));
 	} else {
 		errors.push_back(error);
diff --git a/PTM/t_machine.h b/PTM/t_machine.h
index 5025df49..344aabdf 100644
--- a/PTM/t_machine.h
+++ b/PTM/t_machine.h
@@ -25,6 +25,7 @@ struct t_machine {
 	} text_color;
 	// Input
 	SDL_Keycode last_key_pressed = 0;
+	SDL_Keycode exit_key = 0;
 	// Sound
 	TSound* snd = nullptr;
 	// Comparisons
diff --git a/PTM/t_program_editor.cpp b/PTM/t_program_editor.cpp
index e0d8d818..1ff079db 100644
--- a/PTM/t_program_editor.cpp
+++ b/PTM/t_program_editor.cpp
@@ -390,9 +390,9 @@ void t_program_editor::compile_and_run() {
 void t_program_editor::print_errors(std::vector<string>& errors) {
 	snd->Beep(2500, 100);
 	string error = errors[0];
-	while (running) {
+	while (running || !cfg->autorun.empty()) {
 		draw_screen_base();
-		print_border_top("RUNTIME ERROR", 0);
+		print_border_top("PTM", 0);
 		if (cfg->autorun.empty()) {
 			print_border_bottom("Press ENTER to continue...", 0);
 		} else {