look at me. *look at me.* I'm the gun_base now

now there are no more base guns

last_tyrianlike.p8

@@ -1,5 +1,5 @@
 pico-8 cartridge // http://www.pico-8.com
-version 41
+version 42
 __lua__
 -- vacuum gambit
 -- by kistaro windrider
@@ -18,12 +18,17 @@ function csv(s)
  end
  return ret
 end
+function const_fxn(x)
+ return function()
+  return x
+ end
+end
 
 -- generate standard "overlay"
 -- constructor for type tt.
--- if more is defined, generated
--- new calls more(ret) after
--- ret is definitely not nil
+-- if tt.init is defined, generated
+-- new calls tt.init(ret) after
+-- ret is definitely not nil,
 -- before calling setmetatable.
 -- use to initialize mutables.
 --
@@ -32,8 +37,8 @@ end
 -- object *after* more, because
 -- this works better with the
 -- `more` impls i use.
-function mknew(tt, more)
- local mt,oldnew = {__index=tt},tt.new
+function mknew(tt)
+ local mt,oldnew,more = {__index=tt},tt.new,rawget(tt, "init")
  tt.new=function(ret)
   if(not ret) ret = {}
   if(more) more(ret)
@@ -41,15 +46,18 @@ function mknew(tt, more)
   setmetatable(ret, mt)
   return ret
  end
+ return tt
 end
 
 -- intrusive singly-linked list.
 -- cannot be nested!
-linked_list = {is_linked_list=true}
-mknew(linked_list, function(x)
+linked_list = mknew{
+ is_linked_list=true,
+ init = function(x)
   x.next=nil
   x.tail=x
- end)
+ end,
+}
 
 function linked_list:push_back(x)
  self.tail.next = x
@@ -118,7 +126,7 @@ end
 function _init()
  init_blip_pals()
 	wipe_level()
-	primary_ship.main_gun = zap_gun.new()
+	primary_ship.main_gun = zap_gun_p.new()  -- redundant?
 	load_level(example_level_csv)
 	state = game
 	pal(2,129)
@@ -412,7 +420,7 @@ end
 
 scrollrate = 0.25 --in px/frame
 
-ship_m = {
+ship_m = mknew{
 
  -- ships have no shield by default
  shield = 0,
@@ -437,7 +445,6 @@ ship_m = {
  -- ymin, ymax default to nil
  --   pship needs more constraint 
 }
-mknew(ship_m)
 
 function ship_m:die()
  self.dead = true
@@ -580,16 +587,20 @@ end
 -->8
 -- bullet and gun behaviors
 
-bullet_base = {
- enemyspd = 0.5
-}
-mknew(bullet_base)
+function player_blt_cat()
+ return pbullets
+end
 
-gun_base = { 
+function enemy_blt_cat()
+ return ebullets
+end
+
+bullet_base = mknew{ }
+
+gun_base = mknew{ 
  shoot_ready = -32768,
  icon = 20
 }
-mknew(gun_base)
 
 function bullet_base:hitship(_)
  self:die()
@@ -601,18 +612,10 @@ end
 
 function bullet_base:move()
  self.x += self.dx
- if self.enemy then
-  self.y += self.dy
-  if self.y > 128 then
-   self:die()
-   return true
-  end
- else
-  self.y -= self.dy
-  if self.y < -8*self.height then
-   self:die()
-   return true
-  end
+ self.y += self.dy
+ if (self.y > 128) or (self.y < -8 * self.height) then
+  self:die()
+  return true
  end
  return false
 end
@@ -621,19 +624,20 @@ function bullet_base:draw()
  spr(self.sprite, self.x, self.y, self.width, self.height)
 end
 
-function bullet_base:spawn_at(x, y)
- self.x = x - self.center_x_off
- if self.enemy then
-  self.dx *= self.enemyspd
-  self.dy *= self.enemyspd
-  self.y = y + self.top_y_off
-  ebullets:push_back(self)
- else
-  self.y = y - (8 * self.height) + self.bottom_y_off
-  pbullets:push_back(self)
+-- An `actually_shoot` factory
+-- for trivial guns
+function spawn_one(t)
+ return function(gun, x, y)
+  t.new{}:spawn_at(x, y)
  end
 end
 
+function bullet_base:spawn_at(x, y)
+ self.x = x - self.x_off
+ self.y = y - self.y_off
+ self.category():push_back(self)
+end
+
 function gun_base:shoot(x, y)
  if (lframe < self.shoot_ready) return false
  if self.ammo then
@@ -645,23 +649,12 @@ function gun_base:shoot(x, y)
  return true
 end
 
-function gun_base:actually_shoot(x, y)
- local typ = self.t
- local b = typ.new{
-  enemy = self.enemy,
-  sprite = self.enemy and typ.esprite or typ.psprite,
- }
- b:spawn_at(x, y)
- return true
-end
-
 -->8
 -- bullets and guns
 
-zap = bullet_base.new{
+zap_e = mknew(bullet_base.new{
  --shape
- psprite = 8, --index of player ammo sprite
- esprite = 9, -- index of enemy ammo sprite
+ sprite = 9, --index of enemy ammo sprite
  width = 1, --in 8x8 blocks
  height = 1,
  hurt = { -- hurtbox - where this ship can be hit
@@ -670,33 +663,39 @@ zap = bullet_base.new{
   width = 2,
   height = 8
  },
- center_x_off = 1, -- how to position by ship
- bottom_y_off = 0,
- top_y_off = 0,
+ x_off = 1, -- how to position by ship
+ y_off = 8,
  
  damage = 1,
  dx = 0,  -- px/frame
- dy = 8,
+ dy = 4,
 
- hitship = function(_, _)
-  return true
- end
-}
-mknew(zap)
+ hitship = const_fxn(true),
 
-zap_gun = gun_base.new{
- enemy = false,
+ category = enemy_blt_cat,
+})
+
+zap_p = mknew(zap_e.new{
+ sprite = 8,
+ dy = -8,
+ y_off = 0,
+ category = player_blt_cat,
+})
+
+zap_gun_e = mknew(gun_base.new{
  power = 20, -- power consumed per shot
  cooldown = 0x0.000a, -- frames between shots
  ammo = nil, -- unlimited ammo - main gun
- t = zap -- metatable of bullet to fire
-}
-mknew(zap_gun)
+ actually_shoot = spawn_one(zap_e),
+})
 
-blast = bullet_base.new{
+zap_gun_p = mknew(zap_gun_e.new{
+ actually_shoot = spawn_one(zap_p),
+})
+
+blast = mknew(bullet_base.new{
  --shape
- psprite = 12, --index of player ammo sprite
- esprite = 3, -- index of enemy ammo sprite
+ sprite = 12, --index of player ammo sprite
  width = 1, --in 8x8 blocks
  height = 1,
  hurt = { -- hurtbox - where this ship can be hit
@@ -705,13 +704,12 @@ blast = bullet_base.new{
   width = 6,
   height = 6
  },
- center_x_off = 4, -- how to position by ship
- bottom_y_off = 0,
- top_y_off = 0,
+ x_off = 4, -- how to position by ship
+ y_off = 0,
  
  damage = 4,
  dx = 0,  -- px/frame
- dy = 2,
+ dy = -2,
  awaitcancel = false,
 
  -- disable damage for 2 frames
@@ -736,25 +734,22 @@ blast = bullet_base.new{
     self.awaitcancel = false
    end)
   end
- end
-}
-mknew(blast)
+ end,
+ category=player_blt_cat
+})
 
-blast_gun = gun_base.new{
+blast_gun = mknew(gun_base.new{
  icon = 13,
- enemy = false,
- power = 0, -- ammo, not power
+ power = 0, -- only cost is ammo
  cooldown = 0x0.0020, -- frames between shots
  ammo = 5,
  maxammo = 5,
- t = blast -- type of bullet to fire
-}
-mknew(blast_gun)
+ actually_shoot = spawn_one(blast),
+})
 
-protron = bullet_base.new{
+protron_e = mknew(bullet_base.new{
  --shape
- psprite = 23, --index of player ammo sprite
- esprite = 24, -- index of enemy ammo sprite
+ sprite = 24,
  width = 1, --in 8x8 blocks
  height = 1,
  hurt = { -- hurtbox - where this ship can be hit
@@ -763,56 +758,59 @@ protron = bullet_base.new{
   width = 2,
   height = 2
  },
- center_x_off = 1, -- how to position by ship
- bottom_y_off = 4,
- top_y_off = 0,
+ x_off = 1, -- how to position by ship
+ y_off = 4,
  
  damage = 1,
- dx = 0,  -- px/frame
- dy = 3,
-}
-mknew(protron)
+ dym = 0.5, -- gun sets dy;
+             -- this is mult
+ category = enemy_blt_cat,
+})
 
-protron_gun = gun_base.new{
+protron_p = mknew(protron_e.new{
+ sprite=23,
+ dym = -1,
+ y_off = 0,
+ category=player_blt_cat,
+})
+
+protron_gun_e = mknew(gun_base.new{
  icon = 25,
- enemy = false,
  power = 60,
  cooldown = 0x0.000f, -- frames between shots
  ammo = nil,
  maxammo = nil,
- actually_shoot = function(self, x, y)
-  local sprite = protron.psprite
-  if (self.enemy) sprite=protron.esprite
-  for i=1,3 do
-   local b = protron.new{
-    enemy=self.enemy,
-    sprite=sprite,
-    dx = i,
-    dy = 4-i
-   }
-   b:spawn_at(x,y)
-   local b2 = protron.new{
-    enemy=self.enemy,
-    sprite=sprite,
-    dx = -i,
-    dy = 4-i
-   }
-   b2:spawn_at(x,y)
-  end
-  local bup = protron.new{
-   enemy=self.enemy,
-   sprite=sprite,
-   dy=4
-  }
-  bup:spawn_at(x,y)
- end
-}
-mknew(protron_gun)
+ munition = protron_e
+})
 
-vulcan = bullet_base.new{
+function protron_gun_e:actually_shoot(x, y)
+ local m = self.munition.dym
+ for i=1,3 do
+  local b = self.munition.new{
+   dx = i*m,
+   dy = (4-i)*m,
+  }
+  b:spawn_at(x,y)
+  local b2 = self.munition.new{
+   dx = -i*m,
+   dy = (4-i)*m,
+  }
+  b2:spawn_at(x,y)
+ end
+ local bup = self.munition.new{
+  dx=0,
+  dy=4*m,
+ }
+ bup:spawn_at(x,y)
+end
+
+protron_gun_p = mknew(protron_gun_e.new{
+ munition = protron_p,
+})
+
+vulcan_e = mknew(bullet_base.new{
  --shape
- psprite = 22, --index of player ammo sprite
- esprite = 21, -- index of enemy ammo sprite
+ sprite = 21,
  width = 1, --in 8x8 blocks
  height = 1,
  hurt = { -- hurtbox - where this ship can be hit
@@ -821,39 +819,46 @@ vulcan = bullet_base.new{
   width = 1,
   height = 4
  },
- center_x_off = 0.5, -- how to position by ship
- bottom_y_off = 4,
- top_y_off = 0,
+ x_off = 0.5, -- how to position by ship
+ y_off = 0,
  
  damage = 0.5,
- dx = 0,  -- px/frame
- dy = 4,
-}
-mknew(vulcan)
+ -- dx from gun
+ dy = 2,
+ category=enemy_blt_cat
+})
 
-vulcan_gun = gun_base.new{
+vulcan_p = mknew(vulcan_e.new{
+ sprite=22,
+ y_off = 4,
+ dy = -4,
+ category=player_blt_cat
+})
+
+vulcan_gun_e = mknew(gun_base.new{
  icon = 37,
  enemy = false,
  power = 8,
  cooldown = 0x0.0002, -- frames between shots
  ammo = nil,
  maxammo = nil,
+ munition=vulcan_e,
  dxs = {0.35, -0.35, -0.7, 0.7, 0.35, -0.35},
  xoffs = {1, 0, -1, 1, 0, -1},
  dxidx = 1,
  actually_shoot = function(self, x, y)
-  local sprite = self.enemy and vulcan.esprite or vulcan.psprite
-  local b = vulcan.new{
-   enemy=self.enemy,
-   sprite=sprite,
+  local b = self.munition.new{
    dx = self.dxs[self.dxidx],
   }
   b:spawn_at(self.xoffs[self.dxidx]+x,y)
   self.dxidx += 1
   if (self.dxidx > #self.dxs) self.dxidx = 1
  end
-}
-mknew(vulcan_gun)
+})
+
+vulcan_gun_p = mknew(vulcan_gun_e.new{
+ munition=vulcan_p,
+})
 
 -->8
 --ships, including player
@@ -861,7 +866,7 @@ mknew(vulcan_gun)
 firespark = split"9, 8, 2, 5, 1"
 smokespark = split"13, 13, 5, 5"
 
-player = ship_m.new{
+player = mknew(ship_m.new{
  --shape
  sprite = 1, --index of ship sprite
  size = 1, --all ships are square; how many 8x8 sprites?
@@ -911,21 +916,20 @@ player = ship_m.new{
   end
   --dx, dy, shoot_spec, shoot_main
   return (((b&0x2)>>1) - (b&0x1)) * th, (((b&0x8)>>3) - ((b&0x4)>>2)) * th, (b&0x10) > 0, (b&0x20) > 0
- end
-}
-mknew(player,
- function(p)
-  p.main_gun = zap_gun.new()
+ end,
+
+ init = function(p)
+  p.main_gun = zap_gun_p.new()
   -- ONE HIT MODE
   --
   -- p.hp = 0
   -- p.maxhp = 0
   -- p.shield = 0
   -- p.maxshield = 0
- end
-)
+ end,
+})
 
-frownie = ship_m.new{
+frownie = mknew(ship_m.new{
  --shape
  sprite = 3, --index of ship sprite
  size = 1, --all ships are square; how many 8x8 sprites?
@@ -956,10 +960,9 @@ frownie = ship_m.new{
   if (tstate>=4) dx=self.thrust
   return dx,0,false,false
  end,
-}
-mknew(frownie)
+})
 
-blocky = frownie.new{
+blocky = mknew(frownie.new{
  sprite = 10,
  hp = 1.5,
  hurt = {
@@ -977,10 +980,9 @@ blocky = frownie.new{
   end
   ship_m.ow(self)
  end
-}
-mknew(blocky)
+})
 
-spewy = frownie.new{
+spewy = mknew(frownie.new{
  sprite=26,
  power=-20,
  hurt = {
@@ -997,13 +999,13 @@ spewy = frownie.new{
  act=function(self)
   local dx,dy,shoot_spec=frownie.act(self)
   return dx, dy, shoot_spec, true
+ end,
+ init = function(ship)
+  ship.main_gun=ship.main_gun or protron_gun_e.new{}
  end
-}
-mknew(spewy, function(ship)
- ship.main_gun=ship.main_gun or protron_gun.new{enemy=true}
-end)
+})
 
-chasey = ship_m.new{
+chasey = mknew(ship_m.new{
  sprite = 5,
  size = 1,
  hurt = {
@@ -1026,10 +1028,11 @@ chasey = ship_m.new{
  thrust = 0.2,
  drag = 0.075,
  slip = true,
-}
-mknew(chasey, function(ship)
- ship.main_gun=ship.main_gun or zap_gun.new{enemy=true}
-end)
+
+ init = function(ship)
+  ship.main_gun=ship.main_gun or zap_gun_e.new{}
+ end
+})
 
 function chasey:act()
  self.xmin = max(primary_ship.x-8, 0)
@@ -1037,7 +1040,7 @@ function chasey:act()
  return 0, 0, false, self.x - 16 < primary_ship.x and self.x + 16 > primary_ship.x
 end
 
-xl_chasey=chasey.new{
+xl_chasey=mknew(chasey.new{
  size=2,
  maxspd=1.25,
  hurt = {
@@ -1046,6 +1049,8 @@ xl_chasey=chasey.new{
   width = 12,
   height = 10
  },
+ fire_off_x = 8,
+ fire_off_y = 15,
  hp = 19.5,
  shield = 5,
  boss = true,
@@ -1060,10 +1065,11 @@ xl_chasey=chasey.new{
   sspr(40, 0, 8, 8, self.x, self.y, 16, 16)
   pal()
  end,
-}
-mknew(xl_chasey, function(ship)
- ship.main_gun=ship.main_gun or zap_gun.new{enemy=true}
-end)
+ init = function(ship)
+  ship.main_gun=ship.main_gun or zap_gun_e.new{}
+ end,
+})
+
 -->8
 -- collisions
 
@@ -1077,12 +1083,11 @@ function collides(box1, box2)
 	  or box1.y+box1.height<box2.y)
 end
 
-collider = { }
-mknew(collider,
- function(x)
+collider = mknew{
+ init = function(x)
   x.suppress = {}
- end
-)
+ end,
+}
 
 function collider_indexes(box)
  local ret = {}
@@ -1271,9 +1276,9 @@ end
 
 function spawn_bonus_vulcan_chasey()
  local c = spawn_chasey()
- c.main_gun=vulcan_gun.new{enemy=true}
+ c.main_gun=vulcan_gun_e.new{enemy=true}
  c.die = function(self)
-  spawn_main_gun_at(self.x-1, self.y-1, vulcan_gun)
+  spawn_main_gun_at(self.x-1, self.y-1, vulcan_gun_p)
   chasey.die(self)
  end
  c.sprite=4
@@ -1376,7 +1381,7 @@ example_level_csv=[[1,spawn_frownie
 310,spawn_blocking_blocky
 310,spawn_blocking_blocky
 311,spawn_frownie
-350,spawn_main_gun_at,70,-11,protron_gun
+350,spawn_main_gun_at,70,-11,protron_gun_p
 401,spawn_frownie
 420,spawn_blocking_frownie
 430,spawn_bonus_vulcan_chasey
@@ -1486,8 +1491,9 @@ bullets
   shots much easier to dodge
 * damage - damage per hit;
   used by ships
-* psprite, esprite - index of
-  player or enemy sprite.
+* sprite - sprite index.
+* x_off, y_off - renamed for
+  the next two vars. may revert
 * center_off_x - the horizontal
   centerpoint of the bullet,
   for positioning when firing.
@@ -1776,7 +1782,7 @@ true, they are dropped.
 -->8
 -- standard events
 
-blip_fx = {
+blip_fx = mknew{
  cancel=false
 }
 
@@ -1794,8 +1800,6 @@ function blip_fx:abort()
  self.cancel=true
 end
 
-mknew(blip_fx)
-
 blip_pals = {}
 function init_blip_pals()
  for i=0,15 do
@@ -1830,8 +1834,7 @@ function boom(x,y,boominess,is_boss)
  return
 end
 
-spark_particle={}
-mknew(spark_particle)
+spark_particle=mknew{}
 
 function spark_particle:move()
  if (rnd(4) < 1) self.sidx += 1
@@ -1860,7 +1863,7 @@ end
 -->8
 -- powerups
 
-powerup = bullet_base.new{
+powerup = mknew(bullet_base.new{
  -- animated sprite array: "sprites"
  -- to draw under or over anim,
  -- override draw, draw the
@@ -1876,13 +1879,12 @@ powerup = bullet_base.new{
  -- easy to pick up
  dx = 0,
  dy = 1.5, -- 0.75 after enemyspd
- enemy = true, -- collides with player ship
+ category = enemy_blt_cat, -- collides with player ship
  damage = 0,
  
  anim_speed = 2,
  loop_pause = 30 -- affected by animspeed
-}
-mknew(powerup)
+})
 
 -- sprite indexes for "sheen" animation
 sheen8x8 = split"2,54,55,56,57,58,59,60,61"
@@ -1902,16 +1904,15 @@ function powerup:draw()
      self.width, self.height) 
 end
 
-repair = powerup.new{
+repair = mknew(powerup.new{
  hurt = {
   x_off = -2,
   y_off = -2,
   width = 12,
   height = 12
  },
- center_x_off = 4,
- top_y_off = 0,
- bottom_y_off = 0,
+ x_off = 4,
+ y_off = 0,
  sprites = sheen8x8,
  hitship = function(self, ship)
   if (ship ~= primary_ship) return false
@@ -1922,14 +1923,13 @@ repair = powerup.new{
   spr(53, self.x, self.y, self.width, self.height)
   powerup.draw(self)
  end  
-}
-mknew(repair)
+})
 
 function spawn_repair_at(x, y)
  repair.new():spawn_at(x, y)
 end
 
-gun_swap = powerup.new{
+gun_swap = mknew(powerup.new{
  hurt = {
   x_off = -2,
   y_off = -2,
@@ -1937,9 +1937,8 @@ gun_swap = powerup.new{
   height = 16
  },
  -- gun = gun_type.new{}
- center_x_off = 6,
- top_y_off = 0,
- bottom_y_off = 4,
+ x_off = 6,
+ y_off = 0,
  width = 2,
  height = 2,
  sprites = {64, 66, 68, 70, 72, 74, 76, 78},
@@ -1952,8 +1951,7 @@ gun_swap = powerup.new{
   powerup.draw(self)
   spr(self.gun.icon, self.x+2, self.y+2, 1, 1)
  end
-}
-mknew(gun_swap)
+})
 
 function spawn_main_gun_at(x, y, gunt)
  if (type(gunt)=="string") gunt=_ENV[gunt]

old_readme.md

@@ -0,0 +1,356 @@
+This file contains text that used to be in the cartridge itself, but
+I'm getting increasingly anxious about cartridge space so I'm moving
+it out ot a separate file.
+
+---
+
+main loop sequence
+==================
+1. level_frame
+2. events
+3. merge new_events into events
+4. update bg intangibles
+5. move ships (player first)
+6. move bullets (player first)
+7. calculate collisions
+ 1. pship on eship
+ 2. ebullet on pship
+ 3. pbullet on eship
+8. update fg intangibles
+9. check for end of level
+
+draw order
+----------
+bottom to top:
+1. intangibles_bg
+2. player bullets
+3. player ships
+4. enemy ships
+5. enemy bullets
+6. intangibles_fg
+
+notes
+-----
+intangibles_fg move()s after
+all collisions and other moves
+are processed. if an intangible
+is added to the list as a result
+of a collision or move, it will
+itself be move()d before it is
+drawn.
+
+data-driven items
+=================
+guns and bullets both allow the
+most common behaviors to be
+expressed with data alone.
+ships only need a movement
+algorithm expressed.
+
+guns
+----
+* t - metatable for bullet type.
+  fired once in the bullet's
+  default direction per shot.
+* enemy - if true, fired bullets
+  are flagged as enemy bullets.
+* icon - sprite index of an
+  8x8 sprite to display in the
+  hud when the player has this
+  gun. default is 20, a generic
+  crosshair bullseye thing.
+* cooldown - min frames between
+  shots.
+* ammo, maxammo - permitted
+  number of shots. 0 is empty
+  and unfireable. maxammo = 0
+  will cause a divide by zero
+  so don't do that. if nil,
+  ammo is infinite.
+
+default guns manage ammo and
+cooldown in shoot, then call
+actually_shoot to create the
+projectile. override only
+actually_shoot to change
+projectile logic while keeping
+cooldown and ammo logic.
+
+bullets
+-------
+* dx, dy - movement per frame.
+  player bullets use -dy
+  instead.
+* enemyspd - multiplier for dx
+  and dy on enemy bullets.
+  default is 0.5, making enemy
+  shots much easier to dodge
+* damage - damage per hit;
+  used by ships
+* sprite - sprite index.
+* x_off, y_off - renamed for
+  the next two vars. may revert
+* center_off_x - the horizontal
+  centerpoint of the bullet,
+  for positioning when firing.
+  assume a pixel's coordinates
+  refer to the upper left corner
+  of the pixel; the center of
+  a 2-width bullet with an
+  upper left corner at 0 is 1,
+  not 0.5.
+* top_off_y, bottom_off_y -
+  also for positioning when
+  firing. positive distance from
+  top or bottom edge to image.
+  top_off_y will usually be 0,
+  bottom_off_y will not be when
+  bullets are smaller than
+  the sprite box.
+* width, height - measured in
+  full sprites (8x8 boxes), not
+  pixels. used for drawing.
+
+bullets despawn when above or
+below the screen (player or
+enemy bullets, respectively).
+
+by default, bullets despawn
+when they hit something.
+override hitship to change this.
+
+ships
+____
+
+ships move by calculating
+momentum, then offsetting their
+position by that momentum, then
+clamping their position to the
+screen (horizontally only for
+ships that autoscroll). ships
+that autoscroll (slip==true)
+then slide down by scrollspeed.
+fractional coordinates are ok.
+after movement, ships lose
+momentum (ship.drag along each
+axis). abs(momentum) can't
+exceed ship.maxspeed.
+
+ships gain momentum by acting
+like a player pushing buttons.
+the player ship actually reads
+buttons for this.
+
+act -- returns new acceleration:
+dx, dy, shoot_spec, shoot_main.
+dx and dy are change in momentum
+in px/frame. this is controls
+only -- friction is handled in
+ship:move (`drag` value).
+
+ships hitting another ship take
+1 damage per frame of overlap.
+ships hitting a bullet check
+bullet.damage to find out how
+much damage they take. damage
+is applied to shields, then hp.
+damaged ships flash briefly -
+blue (12) if all damage was
+shielded, white (7) if hp was
+damaged. a ship that then has 0
+or less hp calls self:die() and
+tells the main game loop to
+remove it.
+
+shieldcooldown is the interval
+between restoring shield points.
+shieldpenalty is the delay
+before restoring points after
+any damage, reset to this value
+on every damaging hit (whether
+it is absorbed by the shield or
+not) -- shield behaves like
+halo and other shooters in its
+heritage, where it recovers if
+you avoid damage for a while.
+not that there is any safe cover
+in this kind of game.
+
+ships do not repair hp on their
+own. negative-damage bullets
+are treated as 0, but a bullet
+can choose to repair the ship
+it hits in its own hitship
+method, or otherwise edit it
+(changing weapons, refilling
+weapon ammo). powerups are
+therefore a kind of bullet.
+
+levels
+======
+
+a level is a table mapping
+effective frame number to
+functions. when a level starts,
+it sets lframe ("level frame")
+and distance to 0.
+
+every frame, level_frame
+increments lframe by 0x0.0001.
+then if the level is not frozen,
+it increments distance by 1.0
+and runs the function in the
+level table for exactly that
+frame number (if any). distance
+is therefore "nonfrozen frames",
+and is used to trigger level
+progress. lframe always
+increments. ships are encouraged
+to use lframe to control
+animation and movement, and may
+use distance to react to level
+progress separately from overall
+time. remember to multiply
+lframe-related stuff by 0x0001.
+
+a special sentinel value, eol,
+marks the end of the level.
+(the level engine doesn't know
+when it's out of events, so
+without eol, the level will
+simply have no events forever.)
+when it finds eol, level_frame
+throws away the current level
+and tells the main loop that it
+might be done. the main loop
+agrees the level is over and the
+player has won when the level
+has reached eol and there are
+no more enemy ships, enemy
+bullets, or background events
+remaining. player ships, player
+bullets, and intangibles are
+not counted.
+
+level freezing
+--------------
+the level is frozen when the
+global value freeze > 0.
+generally, something intending
+to block level progress (a
+miniboss, a minigame, etc.)
+increments freeze and prepares
+some means of decrementing it
+when it no longer wants to block
+level progress.
+
+most commonly, we want to block
+until some specific ship or
+group of ships has died. for
+these ships, override ship:die
+to decrement freeze. make sure
+to set ship.dead in any new
+ship:die method so anything else
+looking at it can recognize
+the ship as dead.
+
+for anything else, you probably
+want an event to figure out when
+to unfreeze.
+
+levels start at 1
+-----------------
+
+distance is initialized to 0
+but gets incremented before the
+first time the engine looks for
+events. therefore, the first
+frame of the level executes
+level[1]. since levelframe
+executes before anything else,
+level[1] sets up the first frame
+drawn in the level. the player
+does not see a blank world
+before level[1] runs.
+level[1] can therefore be used
+to reconfigure the player ship,
+set up backgrounds, start music,
+kick off some kind of fade-in
+animation, etc.
+
+
+events
+======
+the global list "events" stores
+0-argument functions which are
+called every frame. if they
+return true, they are removed
+from the list and not run again;
+if they return false, they stay
+and will be called in later
+frames. the level does not end
+while the events table is
+nonempty.
+
+events are most commonly used
+to set up something for later
+(for example, blip uses an event
+to remove the fx_pallete from
+the flashing ship when the blip
+expires), but can also be used
+to implement a "level within a
+level" that does something
+complicated until it's done. if
+you froze the level when
+creating the event, remember
+to thaw it (freeze -= 1) on all
+paths that return true.
+
+to do complex stuff in events,
+use a closure or a metatable
+that specifies __call.
+
+to avoid editing the events
+list while it is being iterated,
+events that create new events
+must add those events to
+new_events rather than events.
+new_events is only valid during
+the "event execution" stage, so
+events created at any other time
+must go directly on events
+without using new_events.
+
+intangibles
+===========
+
+the intangibles_fg and
+intangibles_bg lists contain
+items with :move and :draw.
+like ships and bullets, they
+move during _update60 and
+draw during _draw. they are
+not checked for collisions.
+
+intangibles_bg moves/draws
+before anything else moves or
+draws. intangibles_fg
+moves/draws last. this controls
+whether your intangible object
+draws in front of or behind
+other stuff. you probably want
+intangibles_bg for decorative
+elements and intangibles_fg
+for explosions, score popups,
+etc.
+
+there's no scrolling background
+engine but intangibles_bg could
+be used to create one, including
+using the map (otherwise unused
+in this engine) for the purpose.
+
+intangibles do not prevent the
+level from ending. like bullets
+and ships, if :move returns
+true, they are dropped.

rearm_prototype.p8

@@ -0,0 +1,223 @@
+pico-8 cartridge // http://www.pico-8.com
+version 42
+__lua__
+-- vacuum gambit
+-- by kistaro windrider
+
+-- stdlib
+
+-- generate standard "overlay"
+-- constructor for type tt.
+-- if tt.init is defined, generated
+-- new calls tt.init(ret) after
+-- ret is definitely not nil,
+-- before calling setmetatable.
+-- use to initialize mutables.
+--
+-- if there was a previous new,
+-- it is invoked on the new
+-- object *after* more, because
+-- this works better with the
+-- `more` impls i use.
+function mknew(tt)
+ local mt,oldnew,more = {__index=tt},tt.new,rawget(tt, "init")
+ tt.new=function(ret)
+  if(not ret) ret = {}
+  if(more) more(ret)
+  if(oldnew) oldnew(ret)
+  setmetatable(ret, mt)
+  return ret
+ end
+ return tt
+end
+
+function easeoutbounce(t)
+	local n1=7.5625
+	local d1=2.75
+
+	if (t<1/d1) then
+		return n1*t*t;
+	elseif(t<2/d1) then
+		t-=1.5/d1
+		return n1*t*t+.75;
+	elseif(t<2.5/d1) then
+		t-=2.25/d1
+		return n1*t*t+.9375;
+	else
+		t-=2.625/d1
+		return n1*t*t+.984375;
+	end
+end
+
+-->8
+-- entry points
+function _draw()
+ cls()
+ draw_hud_placeholder()
+ left_pane:draw()
+ right_pane:draw()
+ rearm_pane_instance:draw()
+end
+
+function _init()
+ item=1
+ bfm=1
+ crt_frm = 1
+ left_pane = weapon_pane.new{}
+ right_pane = weapon_pane.new{
+  is_left=false,
+  s = 2,
+  hdr = "vulc",
+  body = "   rate\n\n  faster\n  firing\n   rate",
+  hot = function() return item == 2 end}
+ rearm_pane_instance = rearm_pane.new{hot=function() return item < 0 end}
+end
+
+function _update60()
+ crt_frm += 0.25
+ if (crt_frm >= 9) crt_frm = 1
+ if (btn(3) and item > 0 or btn(2) and item < 0) item = -item
+ if (btn(0)) item = 1
+ if (btn(1)) item = 2
+ if (btn() & 0xF ~= 0) and bfm >= 10 or bfm >= 30 then
+  bfm = 1
+ else
+  bfm += 1
+ end
+
+ if btnp(4) then
+  left_pane.pos = -1
+  right_pane.pos = -1
+  rearm_pane_instance.pos = -1
+ end
+
+ if btnp(5) then 
+  left_pane.pos = 1
+  right_pane.pos = 1
+  rearm_pane_instance.pos = 1
+ end
+
+ left_pane:update()
+ right_pane:update()
+ rearm_pane_instance:update()
+end
+
+function draw_hud_placeholder()
+ rectfill(112, 0, 127, 127,0x56)
+ rect(112,0,127,127,7)
+ line(127,1,127,127,5)
+ line(113,127)
+end
+
+-->8
+-- rearm pane drawing
+
+crt={-91,-166,-2641,-1441,-23041,23295,-20491,24570}
+
+function glow_box(x0, y0, x1, y1, c, cf)
+ for i,v in ipairs{c[1],c[2],c[1],0} do
+  i -= 1
+  rect(x0+i,y0+i,x1-i,y1-i,v)
+ end
+ fillp(crt[crt_frm&0xff])
+ rectfill(x0+4, y0+4, x1-4, y1-4, cf)
+ fillp()
+end
+
+function frame_col(hot)
+ if (not hot) return {4,10}
+ if (bfm<=16) return {14,7}
+ return {2,8}
+end
+
+function draw_weap_opt(x, y, c, s, hdr, body)
+ camera(-x,-y)
+ glow_box(0,0,55,100,c,1)
+ spr(s,5, 5)
+ print(hdr, 13, 8, 7)
+ print(body, 5, 15, 6)
+ camera()
+end
+
+function draw_rearm(c)
+ glow_box(0,101,111,127,c,1)
+ spr(5,15,107,4,2)
+ print("full ammo\nfull shield\n+50% health",54, 106, 6)
+end
+
+-->8
+-- rearm pane objects
+easing_pane = mknew{
+ -- to enter: pos = -1; to exit: pos = 1
+ -- runs for 32 frames in, 16 frames out
+}
+
+function easing_pane:frac()
+ local pos = self.pos
+ if (not pos) return
+ if (pos < 0) return 1-easeoutbounce(1+pos)
+ if (pos > 0) return (1-pos)*(1-pos)
+ return 0
+end
+
+function easing_pane:update()
+ local pos = self.pos
+ if (not pos or pos == 0) return
+ if (pos < 0) pos = min(pos + 0x0.05, 0)
+ if pos > 0 then
+  pos -= 0x0.1
+  if (pos <= 0) pos = nil
+ end
+ self.pos = pos
+end
+
+weapon_pane = mknew(easing_pane.new{
+ is_left = true,
+ s = 1,
+ hdr = "hull",
+ body = "\n    +1\n   max\n  health",
+ hot = function() return item == 1 end,
+})
+
+function weapon_pane:draw()
+ local frac, is_left = self:frac(), self.is_left
+ if (not frac) return
+ camera(
+  frac * (is_left and 55 or -128) + (1-frac) * (is_left and 0 or -56),
+  0)
+ glow_box(0,0,55,100,frame_col(self:hot()),1)
+ spr(self.s,5, 5)
+ print(self.hdr, 13, 8, 7)
+ print(self.body, 5, 15, 6)
+ camera()
+end
+
+rearm_pane = mknew(easing_pane.new{})
+
+function rearm_pane:draw()
+ local frac = self:frac()
+ if (not frac) return
+ camera(0, -28 * frac)
+ glow_box(0,101,111,127,frame_col(self:hot()),1)
+ spr(5,15,107,4,2)
+ print("full ammo\nfull shield\n+50% health",54, 106, 6)
+ camera()
+end
+
+__gfx__
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