1Kommand Commented Source

mis,bom,bas={},{},{}                        -- Initialize tables to store:
                                            --  mis: missiles fired (both enemy and player)
                                            --  bom: explosions (booms)
                                            --  bas: player missile batteries (bases)

tax,tay,kb,sco,shk=64,64,1,0,0              -- Initialize globals:
                                            --  tax, tay: targeting reticule XY
                                            --  kb: flag if player is using keyboard input (1), or mouse input
                                            -- sco: player score (0)
                                            -- shk: screen shake effect amount (0)

for n=0,3 do                                -- Add four player bases at XY positions.
 add(bas,{x=16+n*32,y=120+rnd(5)})          -- Vary Y to give the effect of sized buildings.
end

function _update()                          -- Called every game tick

 shk=max(0,shk-.25)                         -- Decrement shake amount, clamped to zero.    

 for m in all(mis)do                        -- Update missiles:
  m.x,m.y,_b=clp(m.x+cos(m.a)*m.s,          --  Move position by angle (a) at speed (s).
                 m.y+sin(m.a)*m.s)          --  Store if new position is out-of-bounds (_b),
                                            --  ie set _b truthy to destroy the missile.
  m.d-=m.s                                  --  Decrease missile distance by its speed.      

  if(m.d<0)_b=1                             --  If missile distance zeroed: set _b truthy.
                                            --  Only player missiles have sane distances.
                                            --  Enemy missiles have distances beyond the size
                                            --  of the play field (256) and wont hit this
                                            --  condition.

  for b in all(bom)do                       --  Update explosions (inside missile loop!):
   if not m.b and                           --  The current missile is *not* attached to a player base
                                            --  (This allows player missiles to pass through explosions, but enemy missiles get hit).
        dist(b.x-m.x,b.y-m.y)<b.r then      --  Distance from missile (m) to explosion (b) is inside blast radius (r).
    _b=1                                    --  Flag missile for destruction.
    sco+=#bas                               --  Increment score * number of bases.
   end
  end

  if _b then                                --  If missile flagged for destruction.
   if(m.b)m.b.w=nil                         --  Clear attached base's reload flag (w) so it can fire again.
   del(mis,m)                               --  Remove this missile.
   if(m.y>16)boom(m.x,m.y,m.c)              --  Create explosion at missile location
  end                                       --  except for missiles at the very top of the display
 end                                        --  (this fixes explosions auto-propagating "explosively"
                                            --   around wave 22)

 for b in all(bom)do                        -- Update explosions:
  b.r+=.4                                   --  Increase blast radius.
  if(b.r>b.s)del(bom,b)                     --  Remove explosion if blast radius (r) > expected size (s).

  for a in all(bas)do                       --  Test for all bases (inside explosion loop!):
   if b.y>a.y and                           --   Explosion Y > base Y
        dist(b.x-a.x,b.y-a.y)<b.r then      --   Distance from explosion to base is < blast radius.
    boom(a.x,a.y,8)                         --   Create new explosion (red, 8) at base location.
    del(bas,a)                              --   Remove base.
    shk=5                                   --   Set screen shake amount.
   end
  end
 end

 if(#bas==0)return                          -- Stop further updates if player has zero bases.

 if btnp(4,1) then                          -- Input: left shift.
  kb=not kb                                 -- Toggle kb flag.
  poke(0x5f2d,kb and 0x0 or 0x3)            -- Enabled/disable mouse input.
 end

 if btnp(5)then                             -- Input: X button.
  for n=1,6do                               -- Try multiple times:    
   b=rnd(bas)                               --  Pick random base.    
   if not b.w then                          --  Base has no active missile in flight.
    print"\as9x6i0g2eb"                     --  SFX.
    fire(b.x,128,b)                         --  Fire missile from base position and
                                            --  attach base (b) to missile.
    b.w=1                                   --  Flag base as waiting (w) to reload.
    break                                   --  Stop further firings.
   end
  end
 end

 wave=ceil(20*time()/300)                   -- Calculate wave as the product (20) of time passed per 5 mins (300 seconds).
 if(#mis<wave)fire()                        -- Fire enemy missile if number of missiles are less than wave number.
end

function _draw()                            -- Main drawing routine.

 if shk>0then                               -- Shake is truthy.
  cls(1)                                    -- Clear display, helps circumvent artifacts regarding the fade-out effect.
  print"\as8i6x3c4s3c0"                     -- SFX.
  if(#bas==0)boom(rnd(128),128,8+rnd(3))    -- Zero player bases spawns explosions while shaking.
 end

 camera(rnd(shk),rnd(shk))                  -- Apply shake to camera.            

 for i=1,64do                               -- Draw randomly filled circles to give the fade-out effect.
  circfill(rnd(128),rnd(128),4,1)
 end

 line(0,127,128,127,4)                      -- Draws a brown line where bases stand on.
 for b in all(bas)do                        -- Draws each base as a gray rectangle.
  rectfill(b.x-3,b.y,b.x+3,128,6)
 end

 for m in all(mis)do                        -- Draw each missile as a point.
  pset(m.x,m.y,m.c)
 end

 for m in all(bom)do                        -- Draw each explosion as a filled circle.
  circfill(m.x,m.y,m.r,m.c)
 end

 rectfill(0,0,128,6,4)                      -- Print the score & wave on a filled rectangle.
 print("score:"..sco.." wave:"..wave,1,1,6)

 if(#bas==0)then                            -- Print game over message if player has no bases.
  print("earth lost",44,64,8)
  return                                    --  Stop further drawings.
 end

 circ(tax,tay,1,1)                          -- Draw targeting reticule with background color.
                                            -- Prevents artifacts of the reticule moving on-screen
                                            -- with the fade-out effect.

	if kb then                              -- Test keyboard input.    
	 if(btn(0))tax-=4                       -- Offset targeting reticule position.
	 if(btn(1))tax+=4
	 if(btn(2))tay-=4
	 if(btn(3))tay+=4
	else                
	 tax,tay=stat(32),stat(33)              -- Read targeting reticule position from mouse cursor.
 end

 circ(tax,tay,1,7)                          -- Draw updated reticule position.
end

function fire(x,y,b)                        -- Fire a missile, for both enemy and player.
                                            -- Enemy missiles have nil XYB parameters.
 d=x and dist(tax-x,tay-y) or 0x100         -- Distance:
                                            --  For player: Calculate distance to targeting reticule.
                                            --  For enemy: Fixed distance at 256 (0x100).
 a=x and atan2(tax-x,tay-y)                 -- Angle:
                                            --  For player: atan from XY to reticule
                                            --  For enemy: nil
 x,y=x or rnd(126),y or 1                   -- X and Y position:
                                            --  For player: unchanged
                                            --  For enemy: random x, 1 for y
 a=a or atan2(rnd(120)-x,128-y)             -- Angle (re-evaluation):
                                            --  For player: unchanged
                                            --  For enemy: atan from XY to random position on bottom of display
 
 add(mis,{x=x,y=y,a=a,                      -- Add missile to table.
          s=b and 2or.5,d=d,
          c=b and 10 or 8+rnd(8),b=b})
end

function boom(x,y,c)                        -- Add explosion (boom) to table.
 print"\as8i6x3c4s3c0"                      -- SFX
 add(bom,{x=x,y=y,r=1,s=8+rnd(15),c=c})     -- xy: position
end                                         -- r: current radius
                                            -- s: maximum size
                                            -- c: color

function clp(a,b)                           -- Clamp two values to display boundary.
                                            -- Returns both new values and if either of them went outside bounds.
 a=min(128,max(0,a))
 b=min(128,max(0,b))
 return a,b,a==0 or a==128 or b==0 or b==128
end

function dist(a,b)                          -- Get distance between XY deltas.
 return sqrt((abs(a)^2)+(abs(b)^2))
end