diff --git a/CMakeLists.txt b/CMakeLists.txt
index d7883392b80..127159a25ad 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -216,6 +216,8 @@ add_library(${PROJECT_NAME} STATIC
 	src/logo.h
 	src/main_data.cpp
 	src/main_data.h
+	src/maniac_patch.cpp
+	src/maniac_patch.h
 	src/map_data.h
 	src/memory_management.h
 	src/message_overlay.cpp
diff --git a/Makefile.am b/Makefile.am
index b71c4191fd4..57144b3a7aa 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -202,6 +202,8 @@ libeasyrpg_player_a_SOURCES = \
 	src/logo.h \
 	src/main_data.cpp \
 	src/main_data.h \
+	src/maniac_patch.cpp \
+	src/maniac_patch.h \
 	src/map_data.h \
 	src/memory_management.h \
 	src/message_overlay.cpp \
diff --git a/src/game_interpreter.cpp b/src/game_interpreter.cpp
index f842603ebf3..f9e99be61e6 100644
--- a/src/game_interpreter.cpp
+++ b/src/game_interpreter.cpp
@@ -40,6 +40,7 @@
 #include "game_message.h"
 #include "game_pictures.h"
 #include "game_screen.h"
+#include "maniac_patch.h"
 #include "spriteset_map.h"
 #include "sprite_character.h"
 #include "scene_gameover.h"
@@ -1499,8 +1500,8 @@ bool Game_Interpreter::CommandControlVariables(lcf::rpg::EventCommand const& com
 		}
 		case 21:
 			// Expression (Maniac)
-			Output::Warning("ControlVariables: Maniac Patch expressions not supported");
-			return true;
+			value = ManiacPatch::ParseExpression(MakeSpan(com.parameters).subspan(6, com.parameters[5]));
+			break;
 		default:
 			Output::Warning("ControlVariables: Unsupported operand {}", operand);
 			return true;
@@ -1529,8 +1530,9 @@ bool Game_Interpreter::CommandControlVariables(lcf::rpg::EventCommand const& com
 			end = Main_Data::game_variables->Get(com.parameters[2]);
 		} else if (target == 4 && Player::IsPatchManiac()) {
 			// Expression (Maniac)
-			Output::Warning("ControlVariables: Maniac Patch expressions not supported");
-			return true;
+			int idx = com.parameters[1];
+			start = ManiacPatch::ParseExpression(MakeSpan(com.parameters).subspan(idx + 1, com.parameters[idx]));
+			end = start;
 		} else {
 			return true;
 		}
diff --git a/src/maniac_patch.cpp b/src/maniac_patch.cpp
new file mode 100644
index 00000000000..59ab7fece57
--- /dev/null
+++ b/src/maniac_patch.cpp
@@ -0,0 +1,235 @@
+/*
+ * This file is part of EasyRPG Player.
+ *
+ * EasyRPG Player is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * EasyRPG Player is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with EasyRPG Player. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "maniac_patch.h"
+#include "main_data.h"
+#include "game_switches.h"
+#include "game_variables.h"
+#include "output.h"
+
+#include <vector>
+
+namespace {
+	enum class Op {
+		Null = 0,
+		U8,
+		U16,
+		S32,
+		UX8,
+		UX16,
+		SX32,
+		Var = 8,
+		Switch,
+		VarIndirect = 13,
+		SwitchIndirect,
+		Array = 19,
+		Negate = 24,
+		Not,
+		Flip,
+		AssignInplace = 34,
+		AddInplace,
+		SubInplace,
+		MulInplace,
+		DivInplace,
+		ModInplace,
+		BitOrInplace,
+		BitAndInplace,
+		BitXorInplace,
+		BitShiftLeftInplace,
+		BitShiftRightInplace,
+		Add = 48,
+		Sub,
+		Mul,
+		Div,
+		Mod,
+		BitOr,
+		BitAnd,
+		BitXor,
+		BitShiftLeft,
+		BitShiftRight,
+		Equal,
+		GreaterEqual,
+		LessEqual,
+		Greater,
+		Less,
+		NotEqual,
+		Or,
+		And,
+		Range,
+		Subscript,
+		Ternary = 72,
+		Function = 78
+	};
+
+	using Result = std::tuple<std::vector<uint32_t>::iterator, int>;
+}
+
+Result process(std::vector<uint32_t>::iterator it, std::vector<uint32_t>::iterator end) {
+	int value = 0;
+	int imm = 0;
+	int imm2 = 0;
+	int imm3 = 0;
+
+	auto op = static_cast<Op>(*it);
+	++it;
+
+	// When entering the switch it is on the first argument
+	switch (op) {
+		case Op::Null:
+			return {++it, 0};
+		case Op::U8:
+		case Op::UX8:
+			value = *it++;
+			return {it, static_cast<uint8_t>(value)};
+		case Op::U16:
+		case Op::UX16:
+			imm = *it++;
+			imm2 = *it++;
+			value = (imm2 << 8) + imm;
+			return {it, static_cast<uint16_t>(value)};
+		case Op::S32:
+		case Op::SX32:
+			imm = *it++;
+			imm2 = *it++;
+			imm3 = *it++;
+			value = *it++;
+			value = (value << 24) + (imm3 << 16) + (imm2 << 8) + imm;
+			return {it, value};
+		case Op::Var:
+			std::tie(it, imm) = process(it, end);
+			return {it, Main_Data::game_variables->Get(imm)};
+		case Op::Switch:
+			std::tie(it, imm) = process(it, end);
+			return {it, Main_Data::game_switches->GetInt(imm)};
+		case Op::VarIndirect:
+			std::tie(it, imm) = process(it, end);
+			return {it, Main_Data::game_variables->GetIndirect(imm)};
+		case Op::SwitchIndirect:
+			std::tie(it, imm) = process(it, end);
+			return {it, Main_Data::game_switches->GetInt(Main_Data::game_variables->Get(imm))};
+		case Op::Negate:
+			std::tie(it, imm) = process(it, end);
+			return {it, -imm};
+		case Op::Not:
+			std::tie(it, imm) = process(it, end);
+			return {it, !imm ? 0 : 1};
+		case Op::Flip:
+			std::tie(it, imm) = process(it, end);
+			return {it, ~imm};
+		case Op::Add:
+			std::tie(it, imm) = process(it, end);
+			std::tie(it, imm2) = process(it, end);
+			return {it, imm + imm2};
+		case Op::Sub:
+			std::tie(it, imm) = process(it, end);
+			std::tie(it, imm2) = process(it, end);
+			return {it, imm - imm2};
+		case Op::Mul:
+			std::tie(it, imm) = process(it, end);
+			std::tie(it, imm2) = process(it, end);
+			return {it, imm * imm2};
+		case Op::Div:
+			std::tie(it, imm) = process(it, end);
+			std::tie(it, imm2) = process(it, end);
+			if (imm2 == 0) {
+				return {it, 0};
+			}
+			return {it, imm / imm2};
+		case Op::Mod:
+			std::tie(it, imm) = process(it, end);
+			std::tie(it, imm2) = process(it, end);
+			if (imm2 == 0) {
+				return {it, 0};
+			}
+			return {it, imm % imm2};
+		case Op::BitOr:
+			std::tie(it, imm) = process(it, end);
+			std::tie(it, imm2) = process(it, end);
+			return {it, imm | imm2};
+		case Op::BitAnd:
+			std::tie(it, imm) = process(it, end);
+			std::tie(it, imm2) = process(it, end);
+			return {it, imm & imm2};
+		case Op::BitXor:
+			std::tie(it, imm) = process(it, end);
+			std::tie(it, imm2) = process(it, end);
+			return {it, imm ^ imm2};
+		case Op::BitShiftLeft:
+			std::tie(it, imm) = process(it, end);
+			std::tie(it, imm2) = process(it, end);
+			return {it, imm << imm2};
+		case Op::BitShiftRight:
+			std::tie(it, imm) = process(it, end);
+			std::tie(it, imm2) = process(it, end);
+			return {it, imm >> imm2};
+		case Op::Equal:
+			std::tie(it, imm) = process(it, end);
+			std::tie(it, imm2) = process(it, end);
+			return {it, imm == imm2 ? 1 : 0};
+		case Op::GreaterEqual:
+			std::tie(it, imm) = process(it, end);
+			std::tie(it, imm2) = process(it, end);
+			return {it, imm >= imm2 ? 1 : 0};
+		case Op::LessEqual:
+			std::tie(it, imm) = process(it, end);
+			std::tie(it, imm2) = process(it, end);
+			return {it, imm <= imm2 ? 1 : 0};
+		case Op::Greater:
+			std::tie(it, imm) = process(it, end);
+			std::tie(it, imm2) = process(it, end);
+			return {it, imm > imm2 ? 1 : 0};
+		case Op::Less:
+			std::tie(it, imm) = process(it, end);
+			std::tie(it, imm2) = process(it, end);
+			return {it, imm < imm2 ? 1 : 0};
+		case Op::NotEqual:
+			std::tie(it, imm) = process(it, end);
+			std::tie(it, imm2) = process(it, end);
+			return {it, imm != imm2 ? 1 : 0};
+		case Op::Or:
+			std::tie(it, imm) = process(it, end);
+			std::tie(it, imm2) = process(it, end);
+			return {it, !!imm || !!imm2 ? 1 : 0};
+		case Op::And:
+			std::tie(it, imm) = process(it, end);
+			std::tie(it, imm2) = process(it, end);
+			return {it, !!imm && !!imm2 ? 1 : 0};
+		case Op::Subscript:
+			std::tie(it, imm) = process(it, end);
+			std::tie(it, imm2) = process(it, end);
+			return {it, 0};
+		case Op::Ternary:
+			std::tie(it, imm) = process(it, end);
+			std::tie(it, imm2) = process(it, end);
+			std::tie(it, imm3) = process(it, end);
+			return {it, imm != 0 ? imm2 : imm3};
+		default:
+			Output::Warning("Maniac: Expression contains unsupported operation {}", static_cast<int>(op));
+			return {end, 0};
+	}
+}
+
+int32_t ManiacPatch::ParseExpression(Span<const int32_t> op_codes) {
+	std::vector<uint32_t> ops;
+	for (auto &o: op_codes) {
+		ops.push_back((o & 0x000000FF));
+		ops.push_back((o & 0x0000FF00) >> 8);
+		ops.push_back((o & 0x00FF0000) >> 16);
+		ops.push_back((o & 0xFF000000) >> 24);
+	}
+	return std::get<int>(process(ops.begin(), ops.end()));
+}
\ No newline at end of file
diff --git a/src/maniac_patch.h b/src/maniac_patch.h
new file mode 100644
index 00000000000..6e7a5a8c009
--- /dev/null
+++ b/src/maniac_patch.h
@@ -0,0 +1,28 @@
+/*
+ * This file is part of EasyRPG Player.
+ *
+ * EasyRPG Player is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * EasyRPG Player is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with EasyRPG Player. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+
+#ifndef EP_MANIAC_PATCH
+#define EP_MANIAC_PATCH
+
+#include "span.h"
+
+namespace ManiacPatch {
+	int32_t ParseExpression(Span<const int32_t> op_codes);
+}
+
+#endif
\ No newline at end of file