add enemy

src/game.zig

@@ -29,19 +29,47 @@ const Game = @This();
 
 const RNGState = std.Random.DefaultPrng;
 
-const Player = struct {
+const Kinetic = struct {
     pos: Vec2 = .zero,
     vel: Vec2 = .zero,
     acc: Vec2 = .zero,
+
+    const UpdateOptions = struct {
+        max_speed: ?f32 = null,
+        friction: ?f32 = null,
+    };
+
+    pub fn update(self: *Kinetic, dt: f32, opts: UpdateOptions) void {
+        self.vel = self.vel.add(self.acc.multiplyScalar(dt));
+        if (opts.max_speed) |max_speed| {
+            self.vel = self.vel.limitLength(max_speed);
+        }
+        if (opts.friction) |friction| {
+            const friction_force = std.math.pow(f32, 1 - friction, dt);
+            self.vel = self.vel.multiplyScalar(friction_force);
+        }
+        self.pos = self.pos.add(self.vel.multiplyScalar(dt));
+    }
+};
+
+const Player = struct {
+    kinetic: Kinetic = .{},
     last_shot_at: ?Nanoseconds = null
 };
 
 const Bullet = struct {
-    pos: Vec2 = .zero,
-    vel: Vec2 = .zero,
-    size: f32 = 5
+    kinetic: Kinetic,
+    size: f32 = 5,
+    dir: Vec2,
+    speed: f32
 };
 
+const Enemy = struct {
+    kinetic: Kinetic,
+    speed: f32,
+    size: f32,
+}; 
+
 arena: std.heap.ArenaAllocator,
 gpa: Allocator,
 rng: RNGState,
@@ -49,6 +77,7 @@ assets: *Assets,
 
 player: Player = .{},
 bullets: std.ArrayList(Bullet) = .empty,
+enemies: std.ArrayList(Enemy) = .empty,
 
 pub fn init(gpa: Allocator, seed: u64, assets: *Assets) !Game {
     var arena = std.heap.ArenaAllocator.init(gpa);
@@ -59,7 +88,9 @@ pub fn init(gpa: Allocator, seed: u64, assets: *Assets) !Game {
         .gpa = gpa,
         .assets = assets,
         .player = .{
-            .pos = .init(50, 50),
+            .kinetic = .{
+                .pos = .init(50, 50),
+            }
         },
         .rng = RNGState.init(seed),
     };
@@ -68,6 +99,7 @@ pub fn init(gpa: Allocator, seed: u64, assets: *Assets) !Game {
 pub fn deinit(self: *Game) void {
     self.arena.deinit();
     self.bullets.deinit(self.gpa);
+    self.enemies.deinit(self.gpa);
 }
 
 pub fn tick(self: *Game, frame: *Engine.Frame) !void {
@@ -104,16 +136,13 @@ pub fn tick(self: *Game, frame: *Engine.Frame) !void {
     }
     dir = dir.normalized();
 
-    const max_speed = 400;
     const acceleration = 1500;
-    const friction_coef = 0.99988;
 
-    self.player.acc = dir.multiplyScalar(acceleration);
-    self.player.vel = self.player.vel.add(self.player.acc.multiplyScalar(dt));
-    self.player.vel = self.player.vel.limitLength(max_speed);
-    const friction_force = std.math.pow(f32, 1 - friction_coef, dt);
-    self.player.vel = self.player.vel.multiplyScalar(friction_force);
-    self.player.pos = self.player.pos.add(self.player.vel.multiplyScalar(dt));
+    self.player.kinetic.acc = dir.multiplyScalar(acceleration);
+    self.player.kinetic.update(dt, .{
+        .friction = 0.99988,
+        .max_speed = 400
+    });
 
     if (frame.input.mouse_position) |mouse| {
         const cursor_size = Vec2.init(10, 10);
@@ -125,7 +154,7 @@ pub fn tick(self: *Game, frame: *Engine.Frame) !void {
             .color = rgba(255, 200, 200, 0.5)
         });
 
-        const bullet_dir = mouse.sub(self.player.pos).normalized();
+        const bullet_dir = mouse.sub(self.player.kinetic.pos).normalized();
 
         var cooldown_complete = true;
         if (self.player.last_shot_at) |last_shot_at| {
@@ -136,8 +165,21 @@ pub fn tick(self: *Game, frame: *Engine.Frame) !void {
         if (frame.isMouseDown(.left) and cooldown_complete) {
             self.player.last_shot_at = frame.time_ns;
             try self.bullets.append(self.gpa, .{
-                .pos = self.player.pos,
-                .vel = bullet_dir.multiplyScalar(50)
+                .kinetic = .{
+                    .pos = self.player.kinetic.pos,
+                },
+                .dir = bullet_dir,
+                .speed = 50
+            });
+        }
+
+        if (frame.isMousePressed(.right)) {
+            try self.enemies.append(self.gpa, .{
+                .kinetic = .{
+                    .pos = mouse,
+                },
+                .speed = 10,
+                .size = 20
             });
         }
     }
@@ -145,23 +187,38 @@ pub fn tick(self: *Game, frame: *Engine.Frame) !void {
     var size = self.assets.players_tilemap.tile_size;
     frame.drawRectangle(.{
         .rect = .{
-            .pos = self.player.pos.sub(size.divideScalar(2)),
+            .pos = self.player.kinetic.pos.sub(size.divideScalar(2)),
             .size = size,
         },
         .color = rgb(255, 255, 255)
     });
 
     for (self.bullets.items) |*bullet| {
-        bullet.pos = bullet.pos.add(bullet.vel.multiplyScalar(dt));
+        bullet.kinetic.vel = bullet.dir.multiplyScalar(bullet.speed);
+        bullet.kinetic.update(dt, .{});
 
         frame.drawRectangle(.{
             .rect = .{
-                .pos = bullet.pos.sub(.init(bullet.size, bullet.size)),
+                .pos = bullet.kinetic.pos.sub(Vec2.init(bullet.size, bullet.size).multiplyScalar(0.5)),
                 .size = .init(bullet.size, bullet.size),
             },
             .color = rgb(200, 20, 255)
         });
     }
+
+    for (self.enemies.items) |*enemy| {
+        const dir_to_player = self.player.kinetic.pos.sub(enemy.kinetic.pos).normalized();
+        enemy.kinetic.vel = dir_to_player.multiplyScalar(50);
+        enemy.kinetic.update(dt, .{});
+
+        frame.drawRectangle(.{
+            .rect = .{
+                .pos = enemy.kinetic.pos.sub(Vec2.init(enemy.size, enemy.size).multiplyScalar(0.5)),
+                .size = .init(enemy.size, enemy.size),
+            },
+            .color = rgb(20, 200, 20)
+        });
+    }
 }
 
 pub fn debug(self: *Game) !void {