I can't spell

nothing reaches this new logic yet, and multiple steps aren't drawn

vacuum_gambit.p8

@@ -60,7 +60,7 @@ function mknew(tt)
 end
 
 -- intrusive singly-linked list.
--- cannot be nested!
+-- cannot be nested or crossed!
 linked_list = mknew{
  is_linked_list=true,
  init = function(x)
@@ -93,9 +93,7 @@ end
 
 -- strip calls f(x) for each
 -- node, removing each node for
--- which f(x) returns true. it
+-- which f(x) returns true.
--- returns the new tail; nil
--- if the list is now empty.
 function linked_list:strip(f)
  local p, n = self, self.next
  while n do
@@ -107,7 +105,22 @@ function linked_list:strip(f)
   n = n.next
  end
  self.tail = p
- return p
+end
+
+-- stripmove calls x:move() for
+-- each node, removing each node
+-- for which x:move() is true.
+function linked_list:stripmove()
+ local p, n = self, self.next
+ while n do
+  if n:move() then
+   p.next = n.next
+  else
+   p = n
+  end
+  n = n.next
+ end
+ self.tail = p
 end
 
 -- optimized special case -
@@ -188,14 +201,6 @@ function _update60()
  mode:update()
 end
 
-function call_f(x)
- return x:f()
-end
-
-function call_move(x)
- return x:move()
-end
-
 function ones(n)
  local ret = 0
  while n != 0 do
@@ -236,55 +241,49 @@ function updategame()
   current_wave:load(0, 0, min(ones(waves_complete)\2, 4))
  end
  events:vore(new_events)
- events:strip(call_move)
+ for _, lst in ipairs{events, intangibles_bg, eships} do
- for _, lst in ipairs{intangibles_bg, eships, pbullets, ebullets} do
+  lst:stripmove()
-  lst:strip(call_move)
  end
 
+	-- eship collider will be used
+ -- both for pship and pbullets.
+ local eship_collider = collider.new{from=eships}
+
  if not ps.dead then
   ps:move()
   local pbox = hurtbox(ps)
-  eships:strip(function(es)
+  for es in eship_collider:iterate_collisions(pbox) do
-   if(not collides(pbox, hurtbox(es))) return
    ps:hitship(es)
-   return es:hitship(ps)
+   if(es:hitship(ps)) eship_collider:yoink(es)
-  end)
-  ebullets:strip(function(eb)
-   if (not collides(pbox, hurtbox(eb))) return
-   ps:hitbullet(eb)
-   return eb:hitship(ps)
-  end)
- end
-
-	-- many bullets and many enemy ships;
-	-- use bucket collider for efficiency
- local pbullet_collider = collider.new()
- local p, n = pbullets, pbullets.next
- while n do
-  n.prev = p
-  pbullet_collider:insert(n)
-  p = n
-  n = p.next
- end
-
- eships:strip(
-  function(es)
-   for pb in all(pbullet_collider:get_collisions(es)) do
-    if pb:hitship(es) then
-     pbullet_collider:hide(pb)
-     pb.prev.next = pb.next
-     if pb.next then
-      pb.next.prev = pb.prev
-     else
-      pbullets.tail = pb.prev
-     end
-    end
-    if (es:hitbullet(pb)) return true
-   end
   end
- )
+  ebullets:strip(function(eb)
+   local disposition
+   repeat
+    disposition=eb:step()
+    if collides(pbox, hurtbox(eb)) then
+     ps:hitbullet(eb)
+     if (eb:hitship(ps)) return true
+    end
+   until disposition
+   return disposition == "dead"
+  end)
+ else
+  ebullets:strip(function(eb) repeat until eb:step() end)
+ end
+
+ pbullets:strip(function(pb)
+  local disposition
+  repeat
+   disposition=pb:step()
+   for es in eship_collider:iterate_collisions(hurtbox(pb)) do
+    if (es:hitbullet(pb)) eship_collider:yoink(es)
+    if (pb:hitship(es)) return true
+   end
+  until disposition
+  return disposition == "dead"
+ end)
  
- intangibles_fg:strip(call_move)
+ intangibles_fg:stripmove()
 
 	if waves_complete == 32767 and not eships.next and not ebullets.next and not events.next then
 	  game_state = win
@@ -701,9 +700,10 @@ end
 --   default: die, return true.
 --   returns whether to delete
 --   the bullet
--- die -- on-removal event,
+bullet_base = mknew{
---   default no-op
+ steps=1,
-bullet_base = mknew{ }
+ current_step=0
+}
 
 gun_base = mknew{ 
  shoot_ready = -32768,
@@ -826,22 +826,16 @@ remainder:
 end
 
 function bullet_base:hitship(_)
- self:die()
  return true
 end
 
-function bullet_base:die()
+function bullet_base:step()
-end
+ self.current_step=(self.current_step+1)%self.steps
-
-function bullet_base:move()
  self.x += self.dx
  self.y += self.dy
  if (self.f) self.f -= 1
- if (self.y > 145) or (self.y < -8 * self.height) or (self.f and self.f < 0) then
+ if ((self.y > 130) or (self.y < -self.height*8) or (self.f and self.f < 0) or (self.x > 128) or (self.x < -self.width*8)) return "dead"
-  self:die()
+ if (self.current_step == 0) return "stop"
-  return true
- end
- return false
 end
 
 function bullet_base:draw()
@@ -1445,6 +1439,22 @@ end
 collider = mknew{
  init = function(x)
   x.suppress = {}
+  local p, n = x.from, x.from.next
+  while n do
+   -- insert
+   for i in all(collider_indexes(hurtbox(n))) do
+    local a = x[i]
+    if not a then
+     a = {}
+     x[i] = a
+    end
+    add(a, n)
+   end
+   -- prepare yoink
+   n.prev = p
+   p = n
+   n = n.next
+  end
  end,
 }
 
@@ -1458,40 +1468,39 @@ function collider_indexes(box)
  return ret
 end
 
-function collider:insert(item)
+function collider:yoink(item)
- -- todo: separate "big items" list?
- local bdx = collider_indexes(hurtbox(item))
- for i in all(bdx) do
-  local x = self[i]
-  if not x then
-   x = {}
-   self[i] = x
-  end
-  add(x, item)
- end
-end
-
-function collider:hide(item)
  self.suppress[item]=true
+ local p,n = item.prev,item.next
+ p.next = n
+ if n then
+  n.prev = p
+ else
+  self.from.tail = p
+ end
 end
 
-function collider:get_collisions(item)
+function collider:iterate_collisions(box)
- local found = { }
  local seen = { }
- local box = hurtbox(item)
  local bucket_ids = collider_indexes(box)
- for b_idx in all(bucket_ids) do
+ local bii, bidl, bucket, bi, blen = 1, #bucket_ids, false, 1, 0
-  local bucket = self[b_idx]
+ return function()
-  if bucket then
+  while bii <= bidl do
-   for candidate in all(bucket) do
+   if not bucket then
-    if not (seen[candidate] or self.suppress[candidate]) then
+    bucket,blen = self[bucket_ids[bii]],0
-     seen[candidate] = true
+    if (bucket) blen=#bucket
-     if (collides(box, hurtbox(candidate))) add(found, candidate)
-    end
    end
+   while bi <= blen do
+    local candidate = bucket[bi]
+    bi += 1
+    if not seen[candidate] then
+     seen[candidate] = true
+     if (not self.suppress[candidate] and collides(box, hurtbox(candidate))) return candidate
+    end
+   end -- done with this bucket
+   bi=1
+   bii += 1
   end
- end
+ end -- end of closure def
- return found
 end
 
 -->8
@@ -1770,7 +1779,6 @@ function xp_gem:draw()
 end
 
 function xp_gem:move()
- 
  if not primary_ship.dead and abs(self.x + 1 - primary_ship.x - primary_ship.hurt.x_off) <= primary_ship.magnet and abs(self.y + 1 - primary_ship.y - primary_ship.hurt.y_off) <= primary_ship.magnet then
   if (self.x < primary_ship.x + 3) self.x += 1
   if (self.x > primary_ship.x + 5) self.x -= 1
@@ -1780,9 +1788,6 @@ function xp_gem:move()
  return bullet_base.move(self)
 end
 
--- todo: "magnetic" behavior
--- when near player ship
-
 function xp_gem:hitship(ship)
  if (ship ~= primary_ship or primary_ship.dead) return false
  primary_ship.xp += self.val