base sideview physics

inc/conf.h

@@ -1,6 +1,14 @@
 #pragma once
 
-#define TARGET_FPS    60
-#define TILE_SIZE     16
-#define PLAYER_WIDTH  12
-#define PLAYER_HEIGHT 12
+#define TARGET_FPS          60
+#define TILE_SIZE           16
+#define PLAYER_WIDTH        14
+#define PLAYER_HEIGHT       14
+#define GRAVITY             0.2f
+#define AIR_RESISTANCE      0.02f
+#define MAX_WALK_SPEED      2.0f
+#define ACCELERATION_AIR    0.1f
+#define ACCELERATION_GROUND 0.4f
+#define FRICTION_AIR        (ACCELERATION_AIR / MAX_WALK_SPEED)
+#define FRICTION_GROUND     (ACCELERATION_GROUND / MAX_WALK_SPEED)
+#define FRICTION_BREAK      (0.6f / MAX_WALK_SPEED)

src/player.c

@@ -1,5 +1,6 @@
 #include "player.h"
 #include "conf.h"
+#include "input.h"
 #include "level.h"
 #include "util.h"
 #include "vec.h"
@@ -20,7 +21,25 @@ player_init(struct Vec pos)
 void
 player_update(void)
 {
-	self.spd.x = 0.9f;
+	const int on_ground = collide_solid(self.pos.x, self.pos.y + 1);
+	const struct Vec dir = VEC(input_down(K_RIGHT) - input_down(K_LEFT),
+	                           input_down(K_DOWN) - input_down(K_UP));
+
+	/* acceleration & friction */
+	if (on_ground && !dir.x) {
+		self.spd.x *= 1.0f * FRICTION_BREAK;
+	} else {
+		self.spd.x *=
+		    1.0f - (on_ground ? FRICTION_GROUND : FRICTION_AIR);
+		self.spd.x +=
+		    (on_ground ? ACCELERATION_GROUND : ACCELERATION_AIR) *
+		    dir.x;
+	}
+
+	/* resistance & gravity */
+	self.spd.y *= 1.0f - AIR_RESISTANCE;
+	self.spd.y += GRAVITY;
+
 	player_move(player_update_rem());
 }