I am baffled I never noticed this before

the visualization is really helpful for showing me that I fucked up my math

.gitignore

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+.DS_Store
+.vscode/settings.json

autobrake_test.p8

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+pico-8 cartridge // http://www.pico-8.com
+version 41
+__lua__
+
+-- vacuum gambit automatic brake test
+-- by kistaro windrider
+
+function usplit(str)
+ return unpack(split(str))
+end
+function csv(s)
+ local ret = split(s, "\n")
+ for i, v in ipairs(ret) do
+  ret[i] = type(v) == "string" and split(v) or { v }
+ end
+ return ret
+end
+
+-- generate standard "overlay"
+-- constructor for type tt.
+-- if more is defined, generated
+-- new calls more(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, more)
+ local mt, oldnew = { __index = tt }, tt.new
+ tt.new = function(ret)
+  if (not ret) ret = {}
+  if (more) more(ret)
+  if (oldnew) oldnew(ret)
+  setmetatable(ret, mt)
+  return ret
+ end
+end
+
+function _init()
+ pal(1,129,1)
+ the_ship = ship.new()
+ constraints:setup()
+ slomo = 1
+ sloc = 0
+ reroll()
+end
+
+function reroll()
+ frames=0
+ sloc=0
+ the_ship:reroll()
+end
+
+function _update60()
+ if (btnp(4)) reroll()
+ if (btnp(5)) constraints:cycle()
+ if (btnp(3)) slomo <<= 1
+ if (btnp(2)) slomo >>= 1
+ slomo = (slomo < 1) and 1 or (slomo > 8192) and 8192 or slomo
+ sloc += 1
+ if sloc >= slomo then
+  frames += 1
+  the_ship:update()
+  sloc=0
+ end
+end
+
+function _draw()
+ cls(1)
+ constraints:draw()
+ the_ship:draw()
+ print("frames: " .. frames, 4, 64, 7)
+ print("speed: 1/" .. slomo, 8, 70, 7)
+
+ print("thrust: ".. actual_t, 4, 80, 7)
+ meter(80, 80, 128, 84, actual_t/the_ship.thrust/2)
+ print("dx: ".. the_ship.dx, 20, 86, 7)
+ meter(80, 86, 128, 90, the_ship.dx/the_ship.maxspd/2)
+ print("x: "..the_ship.x, 24, 92, 7)
+
+ print("xmin:"..tostr(constraints.xmin), 12, 102, 7)
+ print("xmax:"..tostr(constraints.xmax), 12, 108, 7)
+end
+
+function meter(x0, y0, x1, y1, frac)
+ local c = 11
+ if frac < 0 then
+  frac = -frac
+  c = 8
+ end
+ local range = x1-x0
+ local midpoint = x0 + (range/2)
+ rectfill(x0, y0-1, x0, y1+1, 13)
+ rectfill(midpoint, y0-1, midpoint, y1 + 1, 13)
+ local width = range * frac
+ if (width ~= 0) rectfill(x0, y0, x0 + width, y1, c)
+end
+
+-->8
+-- ship
+
+ship = {
+ maxspd=4,
+ thrust=0.25,
+ drag=0.0625,
+ y=32,
+}
+mknew(ship)
+
+function ship:reroll()
+ self.x=rnd(128)
+ self.dx=rnd(2*self.maxspd)-self.maxspd
+end
+
+function ship:draw()
+ if self.x < -7 then
+  spr(2, 0, self.y-7)
+  spr(2, 0, self.y+8)
+ elseif self.x > 127 then
+  spr(2, 120, self.y-7, 1, 1, true)
+  spr(2, 120, self.y+8, 1, 1, true)
+ else
+  spr(1,self.x,self.y)
+ end
+
+ if (self.dx == 0) return
+ local bd, f = brake_dist(self.dx, self.thrust + self.drag)
+ local bdx = self.x+bd-2
+ spr(3, bdx,self.y-2)
+ print(tostr(f), bdx, self.y - 8, 14)
+end
+
+function calc_velocity(v0, t, vmax, drag)
+ local v1 = v0 + t
+ local sg = sgn(v1)
+ v1 -= sg*drag
+ if (sgn(v1) != sg) return 0
+ if (abs(v1) > vmax) return sg*vmax
+ return v1
+end
+
+function ship:update()
+ local t = btn(0) and -1 or btn(1) and 1 or 0
+ t *= self.thrust
+ t = constraints:constrain(self, t)
+ local s = calc_velocity(self.dx, t, self.maxspd, self.drag)
+
+ self.x += s
+ self.dx = s
+ actual_t = t
+end
+
+-->8
+-- constraints
+
+constraints = {
+ ymin=20,
+ ymax=52,
+ color=10
+}
+
+function constraints:constrain(s, want)
+ self.color=10
+
+ local v1 = calc_velocity(s.dx, want, s.maxspd, s.drag)
+ local bd, bf = brake_dist(v1, s.thrust + s.drag)
+
+ return want
+end
+
+function brake_dist(v0, brake_max)
+ local tri_frames = abs(v0\brake_max)
+ local chunks = tri_frames * (tri_frames - 1) >> 1
+ local chunk_zone = chunks * brake_max
+ local overage = abs(v0) - tri_frames * brake_max
+ return (chunk_zone + overage * (tri_frames + 1)) * sgn(v0), (overage > 0) and tri_frames + 1 or tri_frames
+end
+
+function constraints:cycle()
+ if self.ctype=="bounds" then
+  self.ctype="point"
+ elseif self.ctype=="point" then
+  self.ctype="off"
+ else
+  self.ctype="bounds"
+ end
+ self:setup()
+end
+
+function constraints:setup()
+ if self.ctype=="point" then
+  self.xmin = 64
+  self.xmax = 64
+ elseif self.ctype=="bounds" then
+  self.xmin = 32
+  self.xmax = 96
+ else
+  self.xmin = nil
+  self.xmax = nil
+ end
+end
+
+function constraints:draw()
+ if (not self.xmin) return
+ rect(self.xmin, self.ymin, self.xmax, self.ymax, self.color)
+end
+
+-->8
+-- fx
+
+-- todo: spark ring buffer
+
+__gfx__
+000000008000000000080000a000a000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
+00000000006666000080000009090000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
+00000000067777600800000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
+00000000675555758008888009090000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
+000000006750007508000000a000a000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
+00000000067777500080000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
+00000000005555000008000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000

code-of-conduct.md

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+Trans rights.

genericshmup.p8

@@ -75,7 +75,7 @@ function updategame()
 	edeaths = {}
 	for ip, ps in ipairs(pships) do
 	 for ie, eb in ipairs(ebullets) do
-	  if collides(hurtobx(ps), hurtbox(eb)) then
+	  if collides(hurtbox(ps), hurtbox(eb)) then
 	   if (eb:hitship(ps)) add(edeaths, ie)
 	   if ps:hitbullet(eb) then
 	    add(pdeaths, ip)

the_parser.p8

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+pico-8 cartridge // http://www.pico-8.com
+version 41
+__lua__
+-- the parser
+
+parser = {}
+mknew(parser)
+
+-- calls parse_into with a nop
+-- emit function.
+function parser:parse(str)
+ self:parse_into(str, function() end)
+end
+
+-- read a file of commands and
+-- execute them, emitting the
+-- results from each call into
+-- `emit` as a table per row.
+--
+-- a "command" is a method on
+-- self. a row alternates
+-- commands with args. when
+-- calling a command, it also
+-- gets a table of previous
+-- results as the first arg.
+-- args are split on ','.
+function parser:parse_into(str, emit)
+ for row in all(split(str, "\n")) do
+  local prev = {}
+  local sectors = split(row, ":")
+  for i=1,#sectors,2 do
+   local x = self[sectors[i]](self, prev, usplit(sectors[i+1]))
+   if (x) add(prev, x)
+  end
+  emit(prev)
+ end
+end
+
+-- saves prev[sel] as self.name.
+-- if sel is unspecified, saves
+-- all of prev (as a table).
+function parser:saveas(prev, name, sel)
+ self[name] = sel and prev[sel] or prev
+end
+
+-- returns its args, ignoring
+-- prev. Used to stuff things
+-- into prev. args are packed
+-- if there's multiple.
+function parser:val(_, ...)
+ local ret := pack(...)
+ if (#ret == 1) return ret[1]
+ return ret
+end
+
+function parser:bind(_, fn, ...)
+ local f = self[fn]
+ return function()
+  f(...)
+ end
+end