commit 3bb0a04d4cf33cfcb9817f43bb5212c7f3e0bfe6
Author: Joppe Blondel <joppe@joppeb.nl>
Date:   Sun Mar 8 19:34:12 2026 +0100

    Initial commit

diff --git a/BondGraphLib.mo b/BondGraphLib.mo
new file mode 100644
index 0000000..c5d6ad6
--- /dev/null
+++ b/BondGraphLib.mo
@@ -0,0 +1,195 @@
+package BondGraphLib
+
+    connector BondPort "Bond graph power port"
+        Real e "Effort variable";
+        flow Real f "Flow variable";annotation(
+        Icon(graphics = {Rectangle(lineColor = {0, 0, 127}, fillColor = {0, 0, 127},fillPattern = FillPattern.Solid, extent = {{-60, 60}, {60, -60}})}));
+    end BondPort;
+
+    model J1 "Bond graph 1-junction (common flow, efforts sum to zero)"
+        parameter Integer N(min=1) = 2 "# of power ports";
+        parameter Real s[N] = fill(1.0, N)
+        "Bond orientation signs used in the effort balance";
+        BondPort P[N] "Power ports" annotation(
+        Placement(transformation(origin = {-44, 18}, extent = {{-10, -10}, {10, 10}}), iconTransformation(origin = {0, 80}, extent = {{-10, -10}, {10, 10}})));
+        Real f;
+    equation
+        // Efforts sum to zero, with signs from bond directions
+        sum(s[i] * P[i].e for i in 1:N) = 0;
+
+        // Flows are all equal
+        for i in 2:N loop
+            P[i].f = P[i-1].f;
+        end for;
+        f = P[1].f;
+        annotation(
+        Icon(graphics = {Text(extent = {{-100, 100}, {100, -100}}, textString = "1")}));
+    end J1;
+
+    model J0 "Bond graph 0-junction (common effort, flows sum to zero)"
+        parameter Integer N(min=1) = 2 "# of power ports";
+        parameter Real s[N] = fill(1.0, N)
+        "Bond orientation signs used in the effort balance";
+        BondPort P[N] "Power ports" annotation(
+        Placement(transformation(origin = {-44, 18}, extent = {{-10, -10}, {10, 10}}), iconTransformation(origin = {0, 80}, extent = {{-10, -10}, {10, 10}})));
+        Real e;
+    equation
+        // Flows sum to zero, with signs from bond directions
+        sum(s[i] * P[i].f for i in 1:N) = 0;
+
+        // Efforts are all equal
+        for i in 2:N loop
+            P[i].e = P[1].e;
+        end for;
+        e = P[1].e;
+        annotation(
+        Icon(graphics = {Text(extent = {{-100, 100}, {100, -100}}, textString = "0")}));
+    end J0;
+
+    partial model OnePortPassive "One-port passive bond graph element"
+        BondPort p "Generic power port" annotation(
+        Placement(transformation(origin = {-44, 18}, extent = {{-10, -10}, {10, 10}}), iconTransformation(origin = {0, 80}, extent = {{-10, -10}, {10, 10}})));
+    end OnePortPassive;
+
+    partial model OnePortEnergetic "One-port storage element"
+        extends OnePortPassive annotation(
+        Placement(transformation(origin = {-44, 18}, extent = {{-10, -10}, {10, 10}}), iconTransformation(origin = {0, 80}, extent = {{-10, -10}, {10, 10}})));
+        Real state "Conserved quantity";
+    end OnePortEnergetic;
+
+    model C "Bond graph C element"
+        extends OnePortEnergetic(state(start=q0, fixed=true));
+        parameter Real c(min=0) = 1 "Capacitance";
+        parameter Real q0 = 0 "Initial stored quantity (charge)";
+    equation
+        der(state) = p.f;
+        p.e = state / c;
+        annotation(
+        Icon(graphics = {Text(extent = {{-100, 100}, {100, -100}}, textString = "C")}));
+    end C;
+
+    model I "Bond graph I element"
+        extends OnePortEnergetic(state(start=p0, fixed=true));
+        parameter Real I(min=0) = 1 "Inertance / inductance / mass";
+        parameter Real p0 = 0 "Initial stored quantity (momentum / flux)";
+    equation
+        der(state) = p.e;
+        p.f = state / I;
+        annotation(
+        Icon(graphics = {Text(extent = {{-100, 100}, {100, -100}}, textString = "I")}));
+    end I;
+
+    model R "Bond graph resistor"
+        extends OnePortPassive;
+        parameter Real R(min=0) = 1 "Resistance";
+    equation
+        p.e = R * p.f;
+        annotation(
+        Icon(graphics = {Text(extent = {{-100, 100}, {100, -100}}, textString = "R")}));
+    end R;
+
+    model Se "Effort source"
+        BondPort p annotation(
+        Placement(transformation(origin = {-44, 18}, extent = {{-10, -10}, {10, 10}}), iconTransformation(origin = {80, 0}, extent = {{-10, -10}, {10, 10}})));
+        input Real e0 "Imposed effort";
+    equation
+        p.e = e0;
+        annotation(
+        Icon(graphics = {Text(origin = {-20, 0}, extent = {{-80, 100}, {80, -100}}, textString = "Se")}));
+    end Se;
+
+    model Sf "Flow source"
+        BondPort p annotation(
+        Placement(transformation(origin = {-44, 18}, extent = {{-10, -10}, {10, 10}}), iconTransformation(origin = {80, 0}, extent = {{-10, -10}, {10, 10}})));
+        input Real f0 "Imposed flow";
+    equation
+        p.f = f0;
+        annotation(
+        Icon(graphics = {Text(origin = {-20, 0}, extent = {{-80, 100}, {80, -100}}, textString = "Sf")}));
+    end Sf;
+
+    model TF "Bond graph transformer"
+        BondPort p1 "Port 1" annotation(
+        Placement(transformation(origin = {-44, 18}, extent = {{-10, -10}, {10, 10}}), iconTransformation(origin = {-80, 0}, extent = {{-10, -10}, {10, 10}})));
+        BondPort p2 "Port 2" annotation(
+        Placement(transformation(origin = {-44, 18}, extent = {{-10, -10}, {10, 10}}), iconTransformation(origin = {80, 0}, extent = {{-10, -10}, {10, 10}})));
+
+        parameter Real n = 1 "Transformer ratio";
+    equation
+        p1.e = n * p2.e;
+        p2.f = n * p1.f;
+        annotation(
+        Icon(graphics = {Text(extent = {{-80, 100}, {80, -100}}, textString = "TF")}));
+    end TF;
+
+    model GY "Bond graph gyrator"
+        BondPort p1 "Port 1" annotation(
+        Placement(transformation(origin = {-44, 18}, extent = {{-10, -10}, {10, 10}}), iconTransformation(origin = {-80, 0}, extent = {{-10, -10}, {10, 10}})));
+        BondPort p2 "Port 2" annotation(
+        Placement(transformation(origin = {-44, 18}, extent = {{-10, -10}, {10, 10}}), iconTransformation(origin = {80, 0}, extent = {{-10, -10}, {10, 10}})));
+        parameter Real r = 1 "Gyrator modulus";
+    equation
+        p1.e = r * p2.f;
+        p2.e = r * p1.f;
+        annotation(
+        Icon(graphics = {Text(extent = {{-80, 100}, {80, -100}}, textString = "GY")}));
+    end GY;
+
+    model mSe "Bond graph modulated effort source"
+        BondPort p annotation(
+        Placement(transformation(origin = {-44, 18}, extent = {{-10, -10}, {10, 10}}), iconTransformation(origin = {80, 0}, extent = {{-10, -10}, {10, 10}})));
+        Modelica.Blocks.Interfaces.RealInput e0 "Imposed effort" annotation(
+        Placement(transformation(origin = {-8, -64}, extent = {{-20, -20}, {20, 20}}), iconTransformation(origin = {0, -78}, extent = {{-8, -8}, {8, 8}}, rotation = 90)));
+
+    equation
+        p.e = e0;
+        annotation(
+        Icon(graphics = {Text(origin = {-20, 0}, extent = {{-80, 100}, {80, -100}}, textString = "mSe")}));
+    end mSe;
+
+    model mSf "Bond graph modulated flow source"
+        BondPort p annotation(
+        Placement(transformation(origin = {-44, 18}, extent = {{-10, -10}, {10, 10}}), iconTransformation(origin = {80, 0}, extent = {{-10, -10}, {10, 10}})));
+        Modelica.Blocks.Interfaces.RealInput f0 "Imposed flow" annotation(
+        Placement(transformation(origin = {-8, -64}, extent = {{-20, -20}, {20, 20}}), iconTransformation(origin = {0, -78}, extent = {{-8, -8}, {8, 8}}, rotation = 90)));
+
+    equation
+        p.f = f0;
+        annotation(
+        Icon(graphics = {Text(origin = {-20, 0}, extent = {{-80, 100}, {80, -100}}, textString = "mSf")}));
+    end mSf;
+
+    model mTF "Bond graph modulated transformer"
+        BondPort p1 "Port 1" annotation(
+        Placement(transformation(origin = {-44, 18}, extent = {{-10, -10}, {10, 10}}), iconTransformation(origin = {-80, 0}, extent = {{-10, -10}, {10, 10}})));
+        BondPort p2 "Port 2" annotation(
+        Placement(transformation(origin = {-44, 18}, extent = {{-10, -10}, {10, 10}}), iconTransformation(origin = {80, 0}, extent = {{-10, -10}, {10, 10}})));
+        Modelica.Blocks.Interfaces.RealInput m "Modulation" annotation(
+        Placement(transformation(origin = {-8, -64}, extent = {{-20, -20}, {20, 20}}), iconTransformation(origin = {0, -78}, extent = {{-8, -8}, {8, 8}}, rotation = 90)));
+    equation
+        p1.e = m * p2.e;
+        p2.f = m * p1.f;
+        annotation(
+        Diagram(graphics),
+        Icon(graphics = {Text(extent = {{-60, 100}, {60, -100}}, textString = "mTF")}));
+    end mTF;
+
+    model mGY "Bond graph modulated gyrator"
+        BondPort p1 "Port 1" annotation(
+        Placement(transformation(origin = {-44, 18}, extent = {{-10, -10}, {10, 10}}), iconTransformation(origin = {-80, 0}, extent = {{-10, -10}, {10, 10}})));
+        BondPort p2 "Port 2" annotation(
+        Placement(transformation(origin = {-44, 18}, extent = {{-10, -10}, {10, 10}}), iconTransformation(origin = {80, 0}, extent = {{-10, -10}, {10, 10}})));
+        Modelica.Blocks.Interfaces.RealInput m "Modulation" annotation(
+        Placement(transformation(origin = {-8, -64}, extent = {{-20, -20}, {20, 20}}), iconTransformation(origin = {0, -78}, extent = {{-8, -8}, {8, 8}}, rotation = 90)));
+    equation
+        p1.e = m * p2.f;
+        p2.e = m * p1.f;
+        annotation(
+        Diagram(graphics),
+        Icon(graphics = {Text(extent = {{-60, 100}, {60, -100}}, textString = "mGY")}));
+    end mGY;
+
+    annotation(
+    Icon(graphics = {Text(origin = {50, 0}, extent = {{-50, 100}, {50, -100}}, textString = "R"), Line(origin = {-45.22, 20.19}, points = {{-58.7774, -20.1934}, {21.2226, -20.1934}, {-38.7774, 19.8066}}, thickness = 5), Line(origin = {-9.81, -8.19}, points = {{-10.1934, 48.1934}, {-10.1934, -31.8066}}, thickness = 5)}),
+    uses(Modelica(version = "4.1.0")));
+end BondGraphLib;
diff --git a/BondGraphLib2D.mo b/BondGraphLib2D.mo
new file mode 100644
index 0000000..2c82223
--- /dev/null
+++ b/BondGraphLib2D.mo
@@ -0,0 +1,200 @@
+package BondGraphLib2D
+
+    connector BondPort "Bond graph 2D multibond power port"
+        Real e[2] "Effort vector";
+        flow Real f[2] "Flow vector";annotation(
+        Icon(graphics = {Rectangle(lineColor = {0, 85, 0}, fillColor = {0, 85, 0},fillPattern = FillPattern.Solid, extent = {{-60, 60}, {60, -60}})}));
+    end BondPort;
+
+    model J1 "Bond graph 2D 1-junction (common flow, efforts sum to zero)"
+        parameter Integer N(min=1) = 2 "# of power ports";
+        parameter Real s[N] = fill(1.0, N)
+        "Bond orientation signs used in the effort balance";
+        BondPort P[N] "Power ports" annotation(
+        Placement(transformation(origin = {-44, 18}, extent = {{-10, -10}, {10, 10}}), iconTransformation(origin = {0, 80}, extent = {{-10, -10}, {10, 10}})));
+        Real f[2];
+    equation
+        // Efforts sum to zero, with signs from bond directions
+        for j in 1:2 loop
+            sum(s[i] * P[i].e[j] for i in 1:N) = 0;
+        end for;
+
+        // Flows are all equal
+        for i in 2:N loop
+            P[i].f = P[i-1].f;
+        end for;
+        f = P[1].f;
+        annotation(
+        Icon(graphics = {Text(extent = {{-100, 100}, {100, -100}}, textString = "1", textStyle = {TextStyle.Bold, TextStyle.UnderLine}) }));
+    end J1;
+
+    model J0 "Bond graph 2D 0-junction (common effort, flows sum to zero)"
+        parameter Integer N(min=1) = 2 "# of power ports";
+        parameter Real s[N] = fill(1.0, N)
+        "Bond orientation signs used in the effort balance";
+        BondPort P[N] "Power ports" annotation(
+        Placement(transformation(origin = {-44, 18}, extent = {{-10, -10}, {10, 10}}), iconTransformation(origin = {0, 80}, extent = {{-10, -10}, {10, 10}})));
+        Real e[2];
+    equation
+        // Flows sum to zero, with signs from bond directions
+        for j in 1:2 loop
+            sum(s[i] * P[i].f[j] for i in 1:N) = 0;
+        end for;
+
+        // Efforts are all equal
+        for i in 2:N loop
+            P[i].e = P[1].e;
+        end for;
+        e = P[1].e;
+        annotation(
+        Icon(graphics = {Text(extent = {{-100, 100}, {100, -100}}, textString = "0", textStyle = {TextStyle.Bold, TextStyle.UnderLine}) }));
+    end J0;
+
+    partial model OnePortPassive "One-port passive 2D multibond element"
+        BondPort p "Generic power port" annotation(
+        Placement(transformation(origin = {-44, 18}, extent = {{-10, -10}, {10, 10}}), iconTransformation(origin = {0, 80}, extent = {{-10, -10}, {10, 10}})));
+    end OnePortPassive;
+
+    partial model OnePortEnergetic "One-port 2D multibond storage element"
+        extends OnePortPassive annotation(
+        Placement(transformation(origin = {-44, 18}, extent = {{-10, -10}, {10, 10}}), iconTransformation(origin = {0, 80}, extent = {{-10, -10}, {10, 10}})));
+        Real state[2] "Conserved quantity";
+    end OnePortEnergetic;
+
+    model C "Bond graph 2D C element"
+        extends OnePortEnergetic(state(start=q0, each fixed=true));
+        parameter Real c[2,2] = [1, 0; 0, 1] "Capacitance matrix inverse denominator form";
+        parameter Real q0[2] = {0, 0} "Initial stored quantity (charge)";
+    equation
+        der(state) = p.f;
+        c * p.e = state;
+        annotation(
+        Icon(graphics = {Text(extent = {{-100, 100}, {100, -100}}, textString = "C", textStyle = {TextStyle.Bold, TextStyle.UnderLine}) }));
+    end C;
+
+    model I "Bond graph 2D I element"
+        extends OnePortEnergetic(state(start=p0, each fixed=true));
+        parameter Real I[2,2] = [1, 0; 0, 1] "Inertance / inductance / mass matrix";
+        parameter Real p0[2] = {0, 0} "Initial stored quantity (momentum / flux)";
+    equation
+        der(state) = p.e;
+        I * p.f = state;
+        annotation(
+        Icon(graphics = {Text(extent = {{-100, 100}, {100, -100}}, textString = "I", textStyle = {TextStyle.Bold, TextStyle.UnderLine}) }));
+    end I;
+
+    model R "Bond graph 2D resistor"
+        extends OnePortPassive;
+        parameter Real R[2,2] = [1, 0; 0, 1] "Resistance matrix";
+    equation
+        p.e = R * p.f;
+        annotation(
+        Icon(graphics = {Text(extent = {{-100, 100}, {100, -100}}, textString = "R", textStyle = {TextStyle.Bold, TextStyle.UnderLine}) }));
+    end R;
+
+    model Se "Effort source"
+        BondPort p annotation(
+        Placement(transformation(origin = {-44, 18}, extent = {{-10, -10}, {10, 10}}), iconTransformation(origin = {80, 0}, extent = {{-10, -10}, {10, 10}})));
+        input Real e0[2] "Imposed effort";
+    equation
+        p.e = e0;
+        annotation(
+        Icon(graphics = {Text(origin = {-20, 0}, extent = {{-80, 100}, {80, -100}}, textString = "Se", textStyle = {TextStyle.Bold, TextStyle.UnderLine}) }));
+    end Se;
+
+    model Sf "Flow source"
+        BondPort p annotation(
+        Placement(transformation(origin = {-44, 18}, extent = {{-10, -10}, {10, 10}}), iconTransformation(origin = {80, 0}, extent = {{-10, -10}, {10, 10}})));
+        input Real f0[2] "Imposed flow";
+    equation
+        p.f = f0;
+        annotation(
+        Icon(graphics = {Text(origin = {-20, 0}, extent = {{-80, 100}, {80, -100}}, textString = "Sf", textStyle = {TextStyle.Bold, TextStyle.UnderLine}) }));
+    end Sf;
+
+    model TF "Bond graph 2D transformer"
+        BondPort p1 "Port 1" annotation(
+        Placement(transformation(origin = {-44, 18}, extent = {{-10, -10}, {10, 10}}), iconTransformation(origin = {-80, 0}, extent = {{-10, -10}, {10, 10}})));
+        BondPort p2 "Port 2" annotation(
+        Placement(transformation(origin = {-44, 18}, extent = {{-10, -10}, {10, 10}}), iconTransformation(origin = {80, 0}, extent = {{-10, -10}, {10, 10}})));
+
+        parameter Real n[2,2] = [1, 0; 0, 1] "Transformer ratio matrix";
+    equation
+        p1.e = n * p2.e;
+        transpose(n) * p1.f = p2.f;
+        annotation(
+        Icon(graphics = {Text(extent = {{-80, 100}, {80, -100}}, textString = "TF", textStyle = {TextStyle.Bold, TextStyle.UnderLine}) }));
+    end TF;
+
+    model GY "Bond graph 2D gyrator"
+        BondPort p1 "Port 1" annotation(
+        Placement(transformation(origin = {-44, 18}, extent = {{-10, -10}, {10, 10}}), iconTransformation(origin = {-80, 0}, extent = {{-10, -10}, {10, 10}})));
+        BondPort p2 "Port 2" annotation(
+        Placement(transformation(origin = {-44, 18}, extent = {{-10, -10}, {10, 10}}), iconTransformation(origin = {80, 0}, extent = {{-10, -10}, {10, 10}})));
+        parameter Real r[2,2] = [1, 0; 0, 1] "Gyrator modulus matrix";
+    equation
+        p1.e = r * p2.f;
+        p2.e = transpose(r) * p1.f;
+        annotation(
+        Icon(graphics = {Text(extent = {{-80, 100}, {80, -100}}, textString = "GY", textStyle = {TextStyle.Bold, TextStyle.UnderLine}) }));
+    end GY;
+
+    model mSe "Bond graph modulated effort source"
+        BondPort p annotation(
+        Placement(transformation(origin = {-44, 18}, extent = {{-10, -10}, {10, 10}}), iconTransformation(origin = {80, 0}, extent = {{-10, -10}, {10, 10}})));
+        Modelica.Blocks.Interfaces.RealInput e0[2] "Imposed effort" annotation(
+        Placement(transformation(origin = {-8, -64}, extent = {{-20, -20}, {20, 20}}), iconTransformation(origin = {0, -78}, extent = {{-8, -8}, {8, 8}}, rotation = 90)));
+
+    equation
+        p.e = e0;
+        annotation(
+        Icon(graphics = {Text(origin = {-20, 0}, extent = {{-80, 100}, {80, -100}}, textString = "mSe", textStyle = {TextStyle.Bold, TextStyle.UnderLine}) }));
+    end mSe;
+
+    model mSf "Bond graph modulated flow source"
+        BondPort p annotation(
+        Placement(transformation(origin = {-44, 18}, extent = {{-10, -10}, {10, 10}}), iconTransformation(origin = {80, 0}, extent = {{-10, -10}, {10, 10}})));
+        Modelica.Blocks.Interfaces.RealInput f0[2] "Imposed flow" annotation(
+        Placement(transformation(origin = {-8, -64}, extent = {{-20, -20}, {20, 20}}), iconTransformation(origin = {0, -78}, extent = {{-8, -8}, {8, 8}}, rotation = 90)));
+
+    equation
+        p.f = f0;
+        annotation(
+        Icon(graphics = {Text(origin = {-20, 0}, extent = {{-80, 100}, {80, -100}}, textString = "mSf", textStyle = {TextStyle.Bold, TextStyle.UnderLine}) }));
+    end mSf;
+
+    model mTF "Bond graph modulated transformer"
+        BondPort p1 "Port 1" annotation(
+        Placement(transformation(origin = {-44, 18}, extent = {{-10, -10}, {10, 10}}), iconTransformation(origin = {-80, 0}, extent = {{-10, -10}, {10, 10}})));
+        BondPort p2 "Port 2" annotation(
+        Placement(transformation(origin = {-44, 18}, extent = {{-10, -10}, {10, 10}}), iconTransformation(origin = {80, 0}, extent = {{-10, -10}, {10, 10}})));
+        Modelica.Blocks.Interfaces.RealInput m[2,2] "Modulation" annotation(
+        Placement(transformation(origin = {-8, -64}, extent = {{-20, -20}, {20, 20}}), iconTransformation(origin = {0, -78}, extent = {{-8, -8}, {8, 8}}, rotation = 90)));
+    equation
+        p1.e = m * p2.e;
+        transpose(m) * p1.f = p2.f;
+        annotation(
+        Diagram(graphics),
+        Icon(graphics = {Text(extent = {{-60, 100}, {60, -100}}, textString = "mTF", textStyle = {TextStyle.Bold, TextStyle.UnderLine}) }));
+    end mTF;
+
+    model mGY "Bond graph modulated gyrator"
+        BondPort p1 "Port 1" annotation(
+        Placement(transformation(origin = {-44, 18}, extent = {{-10, -10}, {10, 10}}), iconTransformation(origin = {-80, 0}, extent = {{-10, -10}, {10, 10}})));
+        BondPort p2 "Port 2" annotation(
+        Placement(transformation(origin = {-44, 18}, extent = {{-10, -10}, {10, 10}}), iconTransformation(origin = {80, 0}, extent = {{-10, -10}, {10, 10}})));
+        Modelica.Blocks.Interfaces.RealInput m[2,2] "Modulation" annotation(
+        Placement(transformation(origin = {-8, -64}, extent = {{-20, -20}, {20, 20}}), iconTransformation(origin = {0, -78}, extent = {{-8, -8}, {8, 8}}, rotation = 90)));
+    equation
+        p1.e = m * p2.f;
+        p2.e = transpose(m) * p1.f;
+        annotation(
+        Diagram(graphics),
+        Icon(graphics = {Text(extent = {{-60, 100}, {60, -100}}, textString = "mGY", textStyle = {TextStyle.Bold, TextStyle.UnderLine}) }));
+    end mGY;
+
+    annotation(
+    Icon(graphics = {Text(origin = {50, 0}, extent = {{-50, 100}, {50, -100}}, textString = "R", textStyle = {TextStyle.Bold}), Line(origin = {-45.22, 20.19}, points = {{-58.7774, -20.1934}, {21.2226, -20.1934}, {-38.7774, 19.8066}}, thickness = 5), Line(origin = {-9.81, -8.19}, points = {{-10.1934, 48.1934}, {-10.1934, -31.8066}}, thickness = 5), Line(origin = {-78, 16}, points = {{-26, 0}, {30, 0}}, thickness = 5)}),
+    uses(Modelica(version = "4.1.0")),
+    Diagram(graphics));
+end BondGraphLib2D;
\ No newline at end of file
diff --git a/formatter.py b/formatter.py
new file mode 100644
index 0000000..685b8cf
--- /dev/null
+++ b/formatter.py
@@ -0,0 +1,85 @@
+#!/usr/bin/env python3
+import sys
+import re
+from pathlib import Path
+
+INDENT = " " * 4
+
+CLASS_START_RE = re.compile(
+    r"^\s*(?:partial\s+)?(?:package|model|connector|record|function|block|type|operator)\b"
+)
+
+SECTION_RE = re.compile(
+    r"^\s*(?:equation|algorithm|initial\s+equation|initial\s+algorithm|protected|public)\b"
+)
+
+IF_RE = re.compile(r"^\s*if\b.*\bthen\b")
+ELSEIF_RE = re.compile(r"^\s*elseif\b.*\bthen\b")
+ELSE_RE = re.compile(r"^\s*else\b")
+FOR_RE = re.compile(r"^\s*for\b.*\bloop\b")
+WHEN_RE = re.compile(r"^\s*when\b.*\bthen\b")
+ELSEWHEN_RE = re.compile(r"^\s*elsewhen\b.*\bthen\b")
+
+END_RE = re.compile(r"^\s*end\b")
+
+
+def format_modelica(text: str) -> str:
+    lines = text.replace("\t", "    ").splitlines()
+    out = []
+    indent = 0
+
+    for raw in lines:
+        stripped = raw.strip()
+
+        if not stripped:
+            out.append("")
+            continue
+
+        # Closing constructs outdent before printing
+        if END_RE.match(stripped):
+            indent = max(indent - 1, 0)
+
+        # else / elseif / elsewhen align with matching if/when
+        elif ELSE_RE.match(stripped) or ELSEIF_RE.match(stripped) or ELSEWHEN_RE.match(stripped):
+            indent = max(indent - 1, 0)
+
+        # Sections stay at model level, not one level deeper
+        elif SECTION_RE.match(stripped):
+            indent = max(indent - 1, 0)
+
+        out.append(f"{INDENT * indent}{stripped}")
+
+        # Increase indent only for real blocks
+        if CLASS_START_RE.match(stripped):
+            indent += 1
+        elif IF_RE.match(stripped):
+            indent += 1
+        elif FOR_RE.match(stripped):
+            indent += 1
+        elif WHEN_RE.match(stripped):
+            indent += 1
+        elif ELSEIF_RE.match(stripped) or ELSE_RE.match(stripped) or ELSEWHEN_RE.match(stripped):
+            indent += 1
+        elif SECTION_RE.match(stripped):
+            indent += 1
+
+    return "\n".join(out) + "\n"
+
+
+def main():
+    if len(sys.argv) < 2:
+        print("Usage: python format_mo.py input.mo [output.mo]")
+        sys.exit(1)
+
+    input_file = Path(sys.argv[1])
+    output_file = Path(sys.argv[2]) if len(sys.argv) > 2 else input_file
+
+    text = input_file.read_text(encoding="utf-8")
+    formatted = format_modelica(text)
+    output_file.write_text(formatted, encoding="utf-8")
+
+    print(f"Formatted {output_file}")
+
+
+if __name__ == "__main__":
+    main()
\ No newline at end of file