Battle tricks

THIS PAGE WON'T BE UPDATED. Future updates will be in the sizecoding.org wiki: [http://www.sizecoding.org/wiki/Bytebattles]

This is an evolving list of various useful tricks for delivering the most awesome fatalities in byte battles. Possibly also interesting for TIC-80 sizecoding in general.

General notation

Symbol	Definition
`x`	x-coordinate of a pixel
`y`	y-coordinate of a pixel
`i`	index of a pixel
`s`	alias for math.sin

Basic optimizations

Functions, that are called 3 or more times should be aliased. For example, e=elli with e()e()e() is 3 bytes shorter than elli()elli()elli(). Functions with 5 characters may already benefit from aliasing with 2 calls: r=rectb with r()r() is 1 byte shorter than rectb()rectb().
t=0 with t=t+.1 is 3 bytes shorter than t=time()/399.
for i=0,32639 do x=i%240y=i/240 end is 2-3 bytes shorter than for y=0,135 do for x=0,239 do end end.
(x*x+y*y)^.5 is 6 bytes shorter than math.sqrt(x*x+y*y).
s(w-11) and s(w+8) both approximate math.cos(w), so only math.sin needs to be aliased. s(w-11) is slightly more accurate, with the cost of 1 byte.

One-lining

Most whitespace can be removed from LUA code. For example: x=0y=0 is valid. All new lines can be removed or replaced with space, making the whole code a single line:

function TIC()cls()for i=0,32639 do poke4(i,i)end end

⚠️ Letters a-f and A-F after a number cause problems. a=0b=0 is not valid code. It is advisable to only used one letter variables in the ranges g-z and G-Z from the start; this will make eventual one-lining easier.

Load-function

Function load takes a string of code and returns a function with no named arguments, with the code as its body. It's particularly useful for shortening the TIC function after it's onelined:

TIC=load'cls()for i=0,32639 do poke4(i,i)end'

As a rule of thumb, one-lining and using the load trick can bring a ~ 275 character code down to 256.

load can be even used to minimize a function with parameters: ... returns the parameters. For example, the following saves 3 bytes:

SCN=load'r=...poke(16320,r)'

⚠️ The backlash causes problems when using the load trick. In particular, if you have a string with escaped characters in the original code i.e. print("foo\nbar"), then this needs to be double-escaped: load'print("foo\\nbar")'.

Dithering

If you have a floating point color value, TIC-80 pix and poke functions round it (toward zero). To add dithering, add a small value, between 0 and 1, to the color. The best technique depends whether you have x and y available or only i and how many bytes you can spare:

Expression	Length	Notes
		No dithering
`s(i)*99%1`	9	"random" dithering, quite ugly
`i*481/960%1`	11	chess horse
`(x*2-y%2)%4/4`	13	2x2 block dithering
`(i*2-i//80%2)%4/4`	17	2x2 block dithering (almost), from i only

A quick example demonstrating the 2x2 block dithering:

function TIC()
 cls()
 for i=0,2399 do
  x=i%240
  y=i//240
  poke4(i,x/30+(x*2-y%2)%4/4)
 end
end

Palettes

The following palettes assume that j goes from 0 to 47. Usually there's no need to make a new loop for this: just reuse another loop with j=i%48.

Expression	Length	Notes
`poke(16320+j,j*5)`	17
`poke(16320+j,j%3*j/.4)`	22	Use `(j+1)%3` or `(j+2)%3` for different colors
`poke(16320+j,s(j)^2*255)`	24
`poke(16320+j,s(j/15)*255)`	25	`s(j/15)^2` is less bright

Code for testing palettes:

function TIC()
 cls()
 for j=0,47 do poke(16320+j,s(j/15)*255)end
 for c=0,15 do rect(c*5,0,5,5,c)end
end
s=math.sin

Motion blur

In TIC-80 API, the pix and poke4 functions round numbers towards zero. This can be abused for a motion blur: poke4(i,peek4(i)-.9) maps colors 1 to 15 into one lower value, but value 0 stays at it is. Like so:

function TIC()
 t=time()/9
 circ(t%240,t%136,9,15)
 for i=0,32639 do poke4(i,peek4(i)-.9)end
end

Basic raymarcher

The basic structure for a raymarcher that has not been crunched to keep it readable. The map is bunch of repeated spheres here:

function TIC()
 for i=0,32639 do
  -- ray (u,v,w), not normalized!
  u=i%240/120-1
  v=i/32639-.5
  w=1
  -- camera origo (x,y,z)
  x=3
  y=0
  z=time()/999 -- camera moves with time
  j=0
  repeat
   X=x%6-3 -- domain repetition
   Y=y%6-3
   Z=z%6-3
   -- ray not normalized=>reduce scale
   m=(X*X+Y*Y+Z*Z)^.5/2-1
   x=x+m*u
   y=y+m*v
   z=z+m*w
   j=j+1
  until j>15 or m<.1
  poke4(i,j)
 end
end

vsariola/battletricks