add killing enemies

src/engine/math.zig

@@ -426,6 +426,11 @@ pub const Rect = struct {
         const y_overlap = self.pos.y <= pos.y and pos.y < self.pos.y + self.size.y;
         return x_overlap and y_overlap;
     }
+
+    pub fn hasOverlap(lhs: Rect, rhs: Rect) bool {
+        return (lhs.left() < rhs.right() and lhs.right() > rhs.left()) and
+            (lhs.top() < rhs.bottom() and lhs.bottom() > rhs.top());
+    }
 };
 
 pub const Line = struct {

src/game.zig

@@ -61,13 +61,17 @@ const Bullet = struct {
     kinetic: Kinetic,
     size: f32 = 5,
     dir: Vec2,
-    speed: f32
+    speed: f32,
+
+    dead: bool = false
 };
 
 const Enemy = struct {
     kinetic: Kinetic,
     speed: f32,
     size: f32,
+
+    dead: bool = false
 }; 
 
 arena: std.heap.ArenaAllocator,
@@ -102,6 +106,13 @@ pub fn deinit(self: *Game) void {
     self.enemies.deinit(self.gpa);
 }
 
+fn getCenteredRect(pos: Vec2, size: f32) Rect {
+    return .{
+        .pos = pos.sub(Vec2.init(size, size).multiplyScalar(0.5)),
+        .size = .init(size, size),
+    };
+}
+
 pub fn tick(self: *Game, frame: *Engine.Frame) !void {
     const dt = frame.deltaTime();
 
@@ -184,12 +195,8 @@ pub fn tick(self: *Game, frame: *Engine.Frame) !void {
         }
     }
 
-    var size = self.assets.players_tilemap.tile_size;
     frame.drawRectangle(.{
-        .rect = .{
+        .rect = getCenteredRect(self.player.kinetic.pos, 16),
-            .pos = self.player.kinetic.pos.sub(size.divideScalar(2)),
-            .size = size,
-        },
         .color = rgb(255, 255, 255)
     });
 
@@ -197,11 +204,18 @@ pub fn tick(self: *Game, frame: *Engine.Frame) !void {
         bullet.kinetic.vel = bullet.dir.multiplyScalar(bullet.speed);
         bullet.kinetic.update(dt, .{});
 
+        const bullet_rect = getCenteredRect(bullet.kinetic.pos, bullet.size);
+
+        for (self.enemies.items) |*enemy| {
+            const enemy_rect = getCenteredRect(enemy.kinetic.pos, enemy.size);
+            if (enemy_rect.hasOverlap(bullet_rect)) {
+                enemy.dead = true;
+                bullet.dead = true;
+            }
+        }
+
         frame.drawRectangle(.{
-            .rect = .{
+            .rect = bullet_rect,
-                .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)
         });
     }
@@ -211,14 +225,34 @@ pub fn tick(self: *Game, frame: *Engine.Frame) !void {
         enemy.kinetic.vel = dir_to_player.multiplyScalar(50);
         enemy.kinetic.update(dt, .{});
 
+        const enemy_rect = getCenteredRect(enemy.kinetic.pos, enemy.size);
         frame.drawRectangle(.{
-            .rect = .{
+            .rect = enemy_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)
         });
     }
+
+    {
+        var i: usize = 0;
+        while (i < self.bullets.items.len) {
+            if (self.bullets.items[i].dead) {
+                _ = self.bullets.swapRemove(i);
+            } else {
+                i += 1;
+            }
+        }
+    }
+
+    {
+        var i: usize = 0;
+        while (i < self.enemies.items.len) {
+            if (self.enemies.items[i].dead) {
+                _ = self.enemies.swapRemove(i);
+            } else {
+                i += 1;
+            }
+        }
+    }
 }
 
 pub fn debug(self: *Game) !void {