diff --git a/src/main.cpp b/src/main.cpp
index ad92683..38d1453 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -8,9 +8,9 @@
 #include <cmath>
 
 // Configuration defaults - edit to change default run mode
-#define DEFAULT_CONFIG_FILE "configs/solar_system.txt"
-#define DEFAULT_HEADLESS 0      // 0 = GUI mode, 1 = headless mode
-#define DEFAULT_READABLE 0      // 0 = scientific notation, 1 = human-readable (AU, km/s)
+#define DEFAULT_CONFIG_FILE "configs/test_simple.txt"
+#define DEFAULT_HEADLESS 1      // 0 = GUI mode, 1 = headless mode
+#define DEFAULT_READABLE 1      // 0 = scientific notation, 1 = human-readable (AU, km/s)
 #define DEFAULT_SIM_DAYS 365    // Default simulation duration for headless mode
 
 // Unit conversion constants
@@ -46,133 +46,142 @@ void print_body_readable(CelestialBody* body) {
     print_velocity_readable(body->name, body->velocity);
 }
 
-int main(int argc, char** argv) {
-    // Parse command line arguments (start with macro defaults)
-    const char* config_file = DEFAULT_CONFIG_FILE;
-    bool headless = DEFAULT_HEADLESS;
-    bool readable = DEFAULT_READABLE;
-    int sim_duration_days = DEFAULT_SIM_DAYS;
+struct ProgramArgs {
+    const char* config_file;
+    bool headless;
+    bool readable;
+    int sim_duration_days;
+};
+
+void parse_command_line_args(int argc, char** argv, ProgramArgs* args) {
+    args->config_file = DEFAULT_CONFIG_FILE;
+    args->headless = DEFAULT_HEADLESS;
+    args->readable = DEFAULT_READABLE;
+    args->sim_duration_days = DEFAULT_SIM_DAYS;
 
     for (int i = 1; i < argc; i++) {
         if (strcmp(argv[i], "--headless") == 0 || strcmp(argv[i], "-h") == 0) {
-            headless = true;
+            args->headless = true;
         } else if (strcmp(argv[i], "--readable") == 0 || strcmp(argv[i], "-r") == 0) {
-            readable = true;
+            args->readable = true;
         } else if (strcmp(argv[i], "--days") == 0 && i + 1 < argc) {
-            sim_duration_days = atoi(argv[++i]);
+            args->sim_duration_days = atoi(argv[++i]);
         } else if (argv[i][0] != '-') {
-            config_file = argv[i];
+            args->config_file = argv[i];
         }
     }
+}
 
+void print_startup_info(const ProgramArgs* args) {
     printf("=== Orbital Mechanics Simulation ===\n");
-    printf("Loading configuration: %s\n", config_file);
-    if (headless) {
+    printf("Loading configuration: %s\n", args->config_file);
+    if (args->headless) {
         printf("Mode: Headless (terminal output only)\n");
-        printf("Duration: %d days\n", sim_duration_days);
-        if (readable) {
+        printf("Duration: %d days\n", args->sim_duration_days);
+        if (args->readable) {
             printf("Output: Human-readable units (AU, km/s)\n");
         }
     }
+}
 
-    // Create simulation with time step of 60 seconds
-    const int MAX_BODIES = 100;
-    const double TIME_STEP = 60.0;  // 60 seconds per step
-    SimulationState* sim = create_simulation(MAX_BODIES, TIME_STEP);
+void run_headless_simulation(SimulationState* sim, const ProgramArgs* args) {
+    const double SECONDS_PER_DAY = 86400.0;
+    const double total_time = args->sim_duration_days * SECONDS_PER_DAY;
+    const double output_interval = SECONDS_PER_DAY;
+    double next_output_time = 0.0;
 
-    // Load system configuration
-    if (!load_system_config(sim, config_file)) {
-        printf("Failed to load configuration file\n");
-        destroy_simulation(sim);
-        return 1;
+    CelestialBody* initial_state = (CelestialBody*)malloc(sim->body_count * sizeof(CelestialBody));
+    for (int i = 0; i < sim->body_count; i++) {
+        initial_state[i] = sim->bodies[i];
     }
 
-    // If headless mode, run simulation without rendering
-    if (headless) {
-        const double SECONDS_PER_DAY = 86400.0;
-        const double total_time = sim_duration_days * SECONDS_PER_DAY;
-        const double output_interval = SECONDS_PER_DAY;  // Print status once per day
-        double next_output_time = 0.0;
-
-        printf("\n=== Initial State ===\n");
-        for (int i = 0; i < sim->body_count; i++) {
-            CelestialBody* body = &sim->bodies[i];
-            if (readable) {
-                print_body_readable(body);
-            } else {
-                printf("%s:\n", body->name);
-                printf("  Position: (%.3e, %.3e, %.3e) m\n",
-                       body->position.x, body->position.y, body->position.z);
-                printf("  Velocity: (%.3e, %.3e, %.3e) m/s\n",
-                       body->velocity.x, body->velocity.y, body->velocity.z);
-            }
+    printf("\n=== Initial State ===\n");
+    for (int i = 0; i < sim->body_count; i++) {
+        CelestialBody* body = &sim->bodies[i];
+        if (args->readable) {
+            print_body_readable(body);
+        } else {
+            printf("%s:\n", body->name);
+            printf("  Position: (%.3e, %.3e, %.3e) m\n",
+                   body->position.x, body->position.y, body->position.z);
+            printf("  Velocity: (%.3e, %.3e, %.3e) m/s\n",
+                   body->velocity.x, body->velocity.y, body->velocity.z);
         }
+    }
 
-        printf("\n=== Running Simulation ===\n");
-        while (sim->time < total_time) {
-            update_simulation(sim);
-
-            // Print periodic updates
-            if (sim->time >= next_output_time) {
-                printf("Day %.1f: ", sim->time / SECONDS_PER_DAY);
-                for (int i = 0; i < sim->body_count && i < 3; i++) {
-                    Vec3 pos = sim->bodies[i].position;
-                    double dist = vec3_magnitude(pos);
-                    if (readable) {
-                        double angle_rad = atan2(pos.y, pos.x);
-                        double angle_deg = angle_rad * 180.0 / M_PI;
-                        if (angle_deg < 0.0) angle_deg += 360.0;
-                        printf("%s(r=%.4f AU, θ=%.1f°)  ", sim->bodies[i].name, dist / AU, angle_deg);
-                    } else {
-                        printf("%s=%.3e m  ", sim->bodies[i].name, dist);
-                    }
+    printf("\n=== Running Simulation ===\n");
+    while (sim->time < total_time) {
+        update_simulation(sim);
+
+        if (sim->time >= next_output_time) {
+            printf("Day %.1f: ", sim->time / SECONDS_PER_DAY);
+            for (int i = 0; i < sim->body_count && i < 3; i++) {
+                Vec3 pos = sim->bodies[i].position;
+                double dist = vec3_magnitude(pos);
+                if (args->readable) {
+                    double angle_rad = atan2(pos.y, pos.x);
+                    double angle_deg = angle_rad * 180.0 / M_PI;
+                    if (angle_deg < 0.0) angle_deg += 360.0;
+                    printf("%s(r=%.4f AU, θ=%.1f°)  ", sim->bodies[i].name, dist / AU, angle_deg);
+                } else {
+                    printf("%s=%.3e m  ", sim->bodies[i].name, dist);
                 }
-                printf("\n");
-                next_output_time += output_interval;
             }
+            printf("\n");
+            next_output_time += output_interval;
         }
+    }
 
-        printf("\n=== Final State (Day %.1f) ===\n", sim->time / SECONDS_PER_DAY);
-        for (int i = 0; i < sim->body_count; i++) {
-            CelestialBody* body = &sim->bodies[i];
-            if (readable) {
-                print_body_readable(body);
-            } else {
-                printf("%s:\n", body->name);
-                printf("  Position: (%.3e, %.3e, %.3e) m\n",
-                       body->position.x, body->position.y, body->position.z);
-                printf("  Velocity: (%.3e, %.3e, %.3e) m/s\n",
-                       body->velocity.x, body->velocity.y, body->velocity.z);
-            }
+    printf("\n=== Initial State (Day 0.0) ===\n");
+    for (int i = 0; i < sim->body_count; i++) {
+        CelestialBody* body = &initial_state[i];
+        if (args->readable) {
+            print_body_readable(body);
+        } else {
+            printf("%s:\n", body->name);
+            printf("  Position: (%.3e, %.3e, %.3e) m\n",
+                   body->position.x, body->position.y, body->position.z);
+            printf("  Velocity: (%.3e, %.3e, %.3e) m/s\n",
+                   body->velocity.x, body->velocity.y, body->velocity.z);
         }
+    }
 
-        destroy_simulation(sim);
-        return 0;
-    } else {
-        // Graphical mode
-        // Initialize renderer
-        init_renderer(1280, 720, "Orbital Mechanics Simulation");
-
-        // Setup rendering state
-        RenderState render_state;
-        setup_camera(&render_state);
-
-        // Simulation control variables
-        bool paused = false;
-        double speed_multiplier = 1.0;
-        int physics_steps_per_frame = 100;  // Multiple physics steps per frame for stability
-
-        printf("\nSimulation started!\n");
-        printf("Controls:\n");
-        printf("  Arrow keys: Rotate and zoom camera\n");
-        printf("  Space: Pause/Resume\n");
-        printf("  +/-: Speed up/slow down simulation\n");
-        printf("  I: Toggle info display\n");
-        printf("  ESC: Quit\n\n");
-
-        // Main loop
-        while (!WindowShouldClose()) {
-        // Handle input
+    printf("\n=== Final State (Day %.1f) ===\n", sim->time / SECONDS_PER_DAY);
+    for (int i = 0; i < sim->body_count; i++) {
+        CelestialBody* body = &sim->bodies[i];
+        if (args->readable) {
+            print_body_readable(body);
+        } else {
+            printf("%s:\n", body->name);
+            printf("  Position: (%.3e, %.3e, %.3e) m\n",
+                   body->position.x, body->position.y, body->position.z);
+            printf("  Velocity: (%.3e, %.3e, %.3e) m/s\n",
+                   body->velocity.x, body->velocity.y, body->velocity.z);
+        }
+    }
+
+    free(initial_state);
+}
+
+void run_gui_simulation(SimulationState* sim) {
+    init_renderer(1280, 720, "Orbital Mechanics Simulation");
+
+    RenderState render_state;
+    setup_camera(&render_state);
+
+    bool paused = false;
+    double speed_multiplier = 1.0;
+    int physics_steps_per_frame = 100;
+
+    printf("\nSimulation started!\n");
+    printf("Controls:\n");
+    printf("  Arrow keys: Rotate and zoom camera\n");
+    printf("  Space: Pause/Resume\n");
+    printf("  +/-: Speed up/slow down simulation\n");
+    printf("  I: Toggle info display\n");
+    printf("  ESC: Quit\n\n");
+
+    while (!WindowShouldClose()) {
         if (IsKeyPressed(KEY_SPACE)) {
             paused = !paused;
             printf("Simulation %s\n", paused ? "paused" : "resumed");
@@ -189,10 +198,8 @@ int main(int argc, char** argv) {
             printf("Speed multiplier: %.1fx\n", speed_multiplier);
         }
 
-        // Update camera
         update_camera(&render_state);
 
-        // Update physics (multiple steps per frame)
         if (!paused) {
             int steps = (int)(physics_steps_per_frame * speed_multiplier);
             for (int i = 0; i < steps; i++) {
@@ -200,15 +207,36 @@ int main(int argc, char** argv) {
             }
         }
 
-            // Render
-            render_simulation(sim, &render_state);
-        }
+        render_simulation(sim, &render_state);
+    }
+
+    close_renderer();
+    printf("\nSimulation ended. Final time: %.2f days\n", sim->time / 86400.0);
+}
+
+int main(int argc, char** argv) {
+    ProgramArgs args;
+    parse_command_line_args(argc, argv, &args);
+    print_startup_info(&args);
 
-        // Cleanup
-        close_renderer();
+    // Create simulation with time step of 60 seconds
+    const int MAX_BODIES = 100;
+    const double TIME_STEP = 60.0;  // 60 seconds per step
+    SimulationState* sim = create_simulation(MAX_BODIES, TIME_STEP);
+
+    // Load system configuration
+    if (!load_system_config(sim, args.config_file)) {
+        printf("Failed to load configuration file\n");
         destroy_simulation(sim);
+        return 1;
+    }
 
-        printf("\nSimulation ended. Final time: %.2f days\n", sim->time / 86400.0);
-        return 0;
+    if (args.headless) {
+        run_headless_simulation(sim, &args);
+    } else {
+        run_gui_simulation(sim);
     }
+
+    destroy_simulation(sim);
+    return 0;
 }