diff --git a/Makefile b/Makefile
index 9c13dc3..ec025b4 100644
--- a/Makefile
+++ b/Makefile
@@ -32,4 +32,8 @@ $(TARGET): $(OBJS)
 clean:
 	rm -f $(OBJS) $(TARGET)
 
+run:
+	make
+	./engine_sim
+
 .PHONY: clean
diff --git a/engine/engine.cpp b/engine/engine.cpp
index 0e5d68d..a3cb78f 100644
--- a/engine/engine.cpp
+++ b/engine/engine.cpp
@@ -1,4 +1,5 @@
 #include "engine.h"
+#include "iostream"
 
 void Engine::step(double dt, double load_torque_nm) {
     // TODO: replace with real combustion/friction torque model driven
@@ -17,6 +18,16 @@ double Engine::torque_nm() const {
     return m_torque_nm;
 }
 
+void Engine::set_throttle(double throttle) {
+    m_throttle = throttle;
+}
+
+double Engine::get_throttle() {
+    return m_throttle;
+}
+
 void Engine::reset() {
     m_rpm = 0;
+    m_oil_temp = 0;
+    m_coolant_capacity = 0;
 }
diff --git a/engine/engine.h b/engine/engine.h
index b66f966..49e4bab 100644
--- a/engine/engine.h
+++ b/engine/engine.h
@@ -11,12 +11,24 @@ public:
     double rpm() const;
     double torque_nm() const; // net torque produced this step
 
+    void set_throttle(double throttle);
+    double get_throttle();
     void reset();
 
 private:
     double m_rpm = 0.0;
     double m_torque_nm = 0.0;
 
-    static constexpr double kIdleRpm = 900.0;
+    // Fluids
+    double m_oil_capacity = 0.0;
+    double m_coolant_capacity = 0.0;
+
+    double m_oil_temp = 0.0;
+    double m_coolant_temp = 0.0;
+
+    // User Input
+    double m_throttle = 0.0;
+
+    static constexpr double kIdleRpm = 1700.0;
     static constexpr double kCrankInertiaKgm2 = 0.15; // placeholder
 };
diff --git a/engine/engine.o b/engine/engine.o
index c083d20..2a4f1b9 100644
Binary files a/engine/engine.o and b/engine/engine.o differ
diff --git a/engine_sim b/engine_sim
index 733232b..40ea136 100755
Binary files a/engine_sim and b/engine_sim differ
diff --git a/gui/gui.cpp b/gui/gui.cpp
index f6e702d..4690ff7 100644
--- a/gui/gui.cpp
+++ b/gui/gui.cpp
@@ -136,17 +136,41 @@ void Gui::render(const EngineStats& stats) {
 
     ImGui::Columns(2, "main_columns");
 
-    // --- Left column: primary live readouts ---
+    // --- (0,0): primary live readouts — tach + throttle lever side by side ---
     DrawTachGauge(static_cast<float>(stats.rpm), static_cast<float>(stats.max_rpm),
                   static_cast<float>(stats.redline_rpm), 220.0f);
 
+    ImGui::SameLine();
+    ImGui::VSliderFloat("##throttle_lever", ImVec2(40, 160), &m_throttle_lever, 0.0f, 1.0f, "");
+    // VSliderFloat is only "active" while the mouse is down on it, so
+    // this is the spring-back: anything other than an active drag
+    // resets the lever to closed, including on release.
+    if (!ImGui::IsItemActive()) {
+        m_throttle_lever = 0.0f;
+    }
+    ImGui::SameLine();
+    ImGui::Text("Throttle\n%.0f%%", m_throttle_lever * 100.0f);
+
+    // Row 1 starts here in both columns, so column 1's content below
+    // lines up with column 0's regardless of which column is taller.
+    float row1_y = ImGui::GetCursorPosY();
+
+    // --- (1,0): fuel/power readouts + accessory toggles ---
     ImGui::Text("Fuel Consumption: %.2f L/h", stats.fuel_consumption_lph);
     ImGui::Text("Crank Power: %.2f kW", stats.crank_power_kw);
     ImGui::Text("Output Heat: %.1f J", stats.output_heat_j);
 
+    ImGui::Spacing();
+    ImGui::Separator();
+    ImGui::Text("Accessories");
+    ImGui::Checkbox("Alternator", &m_accessories.alternator);
+    ImGui::Checkbox("A/C", &m_accessories.ac);
+    ImGui::Checkbox("Power Steering", &m_accessories.power_steering);
+
     ImGui::NextColumn();
 
-    // --- Right column: extensible stats list (oil temp, coolant temp, ...) ---
+    // --- (1,1): extensible stats list (oil temp, coolant temp, ...) ---
+    ImGui::SetCursorPosY(row1_y);
     ImGui::Text("Stats");
     ImGui::Separator();
     for (const StatEntry& s : stats.extra_stats) {
diff --git a/gui/gui.h b/gui/gui.h
index 7016093..15f763c 100644
--- a/gui/gui.h
+++ b/gui/gui.h
@@ -28,6 +28,15 @@ struct EngineStats {
     std::vector<StatEntry> extra_stats;
 };
 
+// Which parasitic-load accessories are toggled on, via checkboxes drawn
+// in the left column by render(). Placeholders (Alternator, A/C, Power
+// Steering) until there's an actual load model behind them.
+struct AccessoryState {
+    bool alternator = false;
+    bool ac = false;
+    bool power_steering = false;
+};
+
 class Gui {
 public:
     bool init();                     // create window + ImGui context
@@ -36,6 +45,20 @@ public:
     void end_frame();                 // swap buffers
     void shutdown();
 
+    // Reflects the throttle lever as of the most recent render() call.
+    // Spring-loaded: holds whatever value the drag left it at only
+    // while the mouse is down, and snaps back to 0 the instant it's
+    // released. Read it any time after render() this frame, or before
+    // render() next frame, to feed it into the engine.
+    double throttle() const { return static_cast<double>(m_throttle_lever); }
+
+    // Reflects the checkbox state as of the most recent render() call —
+    // read it any time after render() this frame, or before render()
+    // next frame, to feed accessory load into the engine.
+    const AccessoryState& accessories() const { return m_accessories; }
+
 private:
     GLFWwindow* m_window = nullptr;
+    float m_throttle_lever = 0.0f;
+    AccessoryState m_accessories;
 };
diff --git a/gui/gui.o b/gui/gui.o
index d8fee10..70d2c20 100644
Binary files a/gui/gui.o and b/gui/gui.o differ
diff --git a/imgui.ini b/imgui.ini
index 188241f..f2ea7fd 100644
--- a/imgui.ini
+++ b/imgui.ini
@@ -1,10 +1,15 @@
 [Window][Debug##Default]
 Pos=60,60
 Size=400,400
-LastUsed=20260828
+LastUsed=20260831
 
 [Window][Engine Sim]
 Pos=0,0
 Size=900,600
-LastUsed=20260828
+LastUsed=20260831
+
+[Window][Throttle]
+Pos=20,20
+Size=78,195
+LastUsed=20260831
 
diff --git a/main.cpp b/main.cpp
index fe37c7c..d6f4f49 100644
--- a/main.cpp
+++ b/main.cpp
@@ -40,9 +40,15 @@ int main() {
 
         stats.extra_stats.push_back({"Oil Temp", 0.0, "C"});
         stats.extra_stats.push_back({"Coolant Temp", 0.0, "C"});
+        stats.extra_stats.push_back({"Throttle Position", sim.engine().get_throttle(), "%"});
 
         gui.render(stats);
         gui.end_frame();
+
+        // The lever now lives inline in render()'s window, so it's read
+        // after drawing — this frame's drag feeds next frame's step,
+        // same one-frame lag as gui.accessories().
+        sim.engine().set_throttle(gui.throttle());
     }
 
     gui.shutdown();
diff --git a/main.o b/main.o
index c2b83d0..a10babd 100644
Binary files a/main.o and b/main.o differ