Create a ship object.

src/globals.h

@@ -32,3 +32,5 @@ extern ALLEGRO_DISPLAY *display; ///< The allegro display.
 
 extern int redraw; ///< Whether or not to redraw the screen.
 extern int run; ///< Whether or not to continue running the simulation.
+extern int show_help; ///< Whether or not to show the help info.
+extern int show_info; ///< Whether or not to show simulation info.

src/main.c

@@ -19,9 +19,12 @@
 #include "globals.h"
 #include "display.h"
 #include "event_manager.h"
+#include "ship.h"
 
 int run;
 int redraw;
+int show_help;
+int show_info;
 
 #include <stdio.h>
 #include <allegro5/allegro.h>
@@ -53,9 +56,15 @@ int main() {
 		return 1;
 	}
 
+	// initialize the spaceship at the center of the screen
+	struct ship ship;
+	ship_init(&ship, 400, 300);
+
 	// begin running the simulation
 	run = 1;
 	redraw = 1;
+	show_help = 1;
+	show_info = 1;
 	while(run)
 	{
 		handle_event();
@@ -68,9 +77,18 @@ int main() {
 			 * running at a consistent rate, rather than dependent on random
 			 * events.
 			 */
-			// TODO: run simulation physics
+			ship_update(&ship);
 			al_clear_to_color(al_map_rgb(0, 0, 0));
 			// TODO: run simulation draw functions
+			if(show_info)
+			{
+				// TODO: draw simulation stats
+			}
+
+			if(show_help)
+			{
+				// TODO: draw help information
+			}
 			al_flip_display();
 			redraw = 0;
 		}

src/ship.c

@@ -0,0 +1,81 @@
+/*
+ * Copyright (C) 2018  Ortega Froysa, Nicolás <nortega@themusicinnoise.net>
+ * Author: Ortega Froysa, Nicolás <nortega@themusicinnoise.net>
+ *
+ * This program 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.
+ *
+ * This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "ship.h"
+#include "event_manager.h"
+#include "globals.h"
+
+#ifdef DEBUG
+#	include <stdio.h>
+#endif
+#include <math.h>
+
+#ifndef M_PI
+#	define M_PI 3.14159265f
+#endif
+
+#define ACCEL 5.0f
+#define TURN_ACCEL (M_PI / FPS)  // turn at pi radians / sec
+
+void ship_init(struct ship *ship, int x, int y) {
+	if(!ship)
+	{
+#ifdef DEBUG
+		fprintf(stderr,
+				"ship_init(struct ship*,int,int): invalid ship.\n");
+#endif
+		return;
+	}
+	ship->x = x;
+	ship->y = y;
+	ship->velX = ship->velY = 0;
+	ship->direction = 0;
+}
+
+void ship_update(struct ship *ship) {
+	if(!ship)
+	{
+#ifdef DEBUG
+		fprintf(stderr,
+				"ship_update(struct ship*): invalid ship.\n");
+#endif
+		return;
+	}
+
+	if(key_is_down(KEY_UP))
+	{
+		ship->velX += cos(ship->direction) * ACCEL;
+		ship->velY += sin(ship->direction) * ACCEL;
+	}
+	if(key_is_down(KEY_DOWN))
+	{
+		// moving backwards is slower than moving forward
+		ship->velX -= cos(ship->direction) * (ACCEL / 2);
+		ship->velY -= sin(ship->direction) * (ACCEL / 2);
+	}
+	if(key_is_down(KEY_RIGHT))
+		ship->direction -= TURN_ACCEL;
+	if(key_is_down(KEY_LEFT))
+		ship->direction += TURN_ACCEL;
+
+	// keep direction within bounds
+	if(ship->direction >= M_PI * 2)
+		ship->direction -= M_PI * 2;
+	else if(ship->direction < 0)
+		ship->direction += M_PI * 2;
+}

src/ship.h

@@ -0,0 +1,46 @@
+/*
+ * Copyright (C) 2018  Ortega Froysa, Nicolás <nortega@themusicinnoise.net>
+ * Author: Ortega Froysa, Nicolás <nortega@themusicinnoise.net>
+ *
+ * This program 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.
+ *
+ * This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+struct ship {
+	float x, y; ///< The x and y coordinates of the ship.
+	float velX, velY; ///< The x and y velocities of the ship.
+	/**
+	 * The direction that the ship is facing in radians, where
+	 * 0 is right facing.
+	 */
+	float direction;
+};
+
+/**
+ * @brief Initialize the ship at a position.
+ *
+ * @param ship A pointer to the ship object.
+ * @param x Initial x position of the ship.
+ * @param y Initial y position of the ship.
+ */
+void ship_init(struct ship *ship, int x, int y);
+
+/**
+ * @brief Updates the ship's variables according to keyboard
+ * input.
+ *
+ * @param ship A pointer to the ship object.
+ */
+void ship_update(struct ship *ship);