diff --git a/vacuum_gambit.p8 b/vacuum_gambit.p8
index 7b02fc5..c0eef2e 100644
--- a/vacuum_gambit.p8
+++ b/vacuum_gambit.p8
@@ -678,6 +678,11 @@ gun_base = mknew{
  shoot_ready = -32768,
  icon = 20,
  ammobonus = 1,
+
+ -- fractional frames of
+ -- cooldown reduction from
+ -- upgrades, not yet applied
+ cd_remainder = 0,
 }
 
 -- gun_base subtypes are
@@ -727,7 +732,9 @@ function gun_base:ammo_upgrade_opt()
   hdr=self.hdr,
   body=[[----------AMMO
 
- more shots.
+ more shots
+ before you
+  run out.
 
    is: ]]..tostr(a)..[[
   add: ]]..tostr(x)..[[
@@ -740,6 +747,34 @@ total: ]]..tostr(a+x),
  }
 end
 
+function gun_base:rate_upgrade_opt()
+ local c=self.cooldown<<16
+ local rawnewc=0.85*(c-self.cd_remainder)
+ local newc=ceil(rawnewc)
+ return {
+  icon=self.icon,
+  hdr=self.hdr,
+  body=[[----------RATE
+
+reduce delay
+between shots
+  in frames.
+
+  fractions
+add up across
+  upgrades.
+
+   is: ]]..tostr(c)..[[
+minus: ]]..tostr(c-newc)..[[
+----------
+total: ]]..tostr(newc),
+  action=function()
+   self.cooldown=newc>>16
+   self.cd_remainder=newc-rawnewc
+  end,
+ }
+end
+
 function bullet_base:hitship(_)
  self:die()
  return true