Very naive knockback

3 files changed, 53 insertions, 6 deletions

diff --git a/collisions.lua b/collisions.lua
index 4b9c430..04575c4 100644
--- a/collisions.lua
+++ b/collisions.lua
@@ -9,8 +9,11 @@ function is_colliding(a, b)
 end
 
 function handle_collision(a, b)
-    if b.entity_type == Entities.Enemy then
-        print(b.id, b.id * 10, b.id * 10)
+    if a.damage and b.health then
+        if b:is_in_iframe() then
+            return
+        end
+        b:take_damage(a.line_of_sight, a.damage)
     end
 end
 
diff --git a/dyl.lua b/dyl.lua
index e379ae3..bd024ef 100644
--- a/dyl.lua
+++ b/dyl.lua
@@ -31,6 +31,7 @@ enemy = entity()
 function enemy:transition_state()
 end
 enemy:b_type(Entities.Enemy)
+    :b_health(100)
     :b_position(vec2(30, 40))
     :b_sprite_position(vec2(30, 30))
     :b_line_of_sight(vec2(1, 0))
@@ -100,16 +101,18 @@ bow:b_type(Entities.Bow)
 
 sword = entity()
 _attack_burst_sec = 0.200
+_sword_damage = { amount = 2, knockback = { magnitude = 200, time = 0.080 } }
 function sword:transition_state()
     if button_just_pressed(5) and self.state == States.Equipped and self.state_stopwatch > _attack_burst_sec then
         self:transition_to(States.Slashing)
         spawn_slashing_particle(self)
+        self.damage = _sword_damage
     elseif self.state == States.Slashing and self.state_stopwatch > _slashing_timer_sec then
+        self.damage = nil
         self:transition_to(States.Equipped)
     end
 end
-sword
-    :b_type(Entities.Sword)
+sword:b_type(Entities.Sword)
     :b_line_of_sight(vec2(1, 0))
     :b_position(vec2(0, 0))
     :b_sprite_position(vec2(0, 0))
diff --git a/entity.lua b/entity.lua
index caa5226..5cb52d8 100644
--- a/entity.lua
+++ b/entity.lua
@@ -29,6 +29,14 @@ function Entity:b_state(name)
     self.state_stopwatch = 0
     return self
 end
+function Entity:b_health(health)
+    self.health = health
+    return self
+end
+function Entity:b_damage(damage_spec)
+    self.damage = damage_spec
+    return self
+end
 function Entity:b_render_order(ord)
     self.render_order = ord
     return self
@@ -69,6 +77,10 @@ function Entity:build()
     assert(self.state_stopwatch)
 end
 
+function Entity:is_in_iframe()
+    return self.knockback ~= nil and self.knockback.time >= 0
+end
+
 function Entity:transition_to(state_name)
     assert(self.states[state_name])
     if self.state ~= state_name then
@@ -99,6 +111,9 @@ function Entity:update(dt)
     if self.life_time ~= nil then
         self.life_time -= dt
     end
+    if self.life ~= nil and self.life <= 0 then
+        self:kill()
+    end
 end
 
 function Entity:update_line_of_sight()
@@ -109,10 +124,11 @@ end
 
 -- prevent cobblestoning during non-manhattan movement by "lagging" the sprite
 -- behind the actual physical position
+-- this part was painful.
 function Entity:update_sprite_position()
     if self.sprite_position == nil then return end
 
-    -- step in only x or y. trivial
+    -- step in only x or y. trivial.
     if self.velocity == nil or self.velocity.y == 0 or self.velocity.x == 0 then
         self.sprite_position.x = self.position.x
         self.sprite_position.y = self.position.y
@@ -152,9 +168,34 @@ function Entity:update_sprite_position()
     return self
 end
 
+function Entity:take_damage(direction, damage_spec)
+    if self.health == nil then
+        return
+    end
+    self.health -= damage_spec.amount
+    if damage_spec.knockback ~= nil then
+        self.knockback = {
+            velocity = direction * damage_spec.knockback.magnitude,
+            remaining_time = damage_spec.knockback.time,
+            time = damage_spec.knockback.time
+        }
+    end
+end
+
 function Entity:integrate(dt)
     self.state_stopwatch += dt
-    if (self.velocity != nil) then
+
+    if self.knockback ~= nil then
+        if self.knockback.remaining_time <= 0 then
+            self.knockback = nil
+            self.velocity = vec2(0, 0)
+        else
+            self.velocity = self.knockback.velocity * (self.knockback.remaining_time / self.knockback.time)
+            self.knockback.remaining_time -= dt
+        end
+    end
+
+    if self.velocity ~= nil then
         self.position = self.position + (self.velocity * dt)
     end
 end