life4.lua

-- title:  game title
-- author: game developer
-- desc:   short description
-- script: lua

local GW = 240
local GH = 136

-- current state address / previous state address
local ADRC = 0x8000
local ADRP = 0xBFC0 -- half way between 0x8000 and 0xFF80 (input)
-- local ADRP = 0xFF8C -- after input

local ADRC2 = ADRC*2 -- x2 for poke4/peek4
local ADRP2 = ADRP*2

function init()
    memset(ADRC, 0x00, GW//2*GH)
    rand_cells()
end

function TIC()
    if     btnp(4) then fill_grid(true)
    elseif btnp(5) then fill_grid(false)
    elseif btnp(6) then rand_cells() end

    -- cls(13) -- redundant since I'm poking the screen mem directly
    next_gen()
    draw()
end

function draw()
    for j=0, GH-1 do
        for i=0, GW-1 do
            local idx_A = ADRC2+(i+j*GW)
            local A = peek4(idx_A) & 1
            local scridx = i+j*240

            if A == 1 then poke4(scridx, 9)
            else           poke4(scridx, 0) end
        end
    end
end

function fill_grid(fill)
    if fill then memset(ADRC, 0xFF, (GW//2)*GH)
    else         memset(ADRC, 0x00, (GW//2)*GH) end
end

function rand_cells()
    for j=0, GH-1 do
        for i=0, GW-1, 2 do
            local idx_A = ADRC2+(i+j*GW)
            local rA = math.random()
            if rA < 0.5 then poke4(idx_A, 0)
            else             poke4(idx_A, 1) end

            local idx_B = idx_A+1
            local rB = math.random()
            if rB < 0.5 then poke4(idx_B, 0)
            else             poke4(idx_B, 1) end
        end
    end
    count_neighbors()
end

function count_neighbors()
    memcpy(ADRP, ADRC, (GW/2)*GH)

    for j=0, GH-1 do
        for i=0, GW-1, 2 do
            local idx = i+j*GW
            local idx_A = ADRC2+idx
            local idx_B = idx_A+1
            local A, B = peek4(idx_A), peek4(idx_B)

            local idx_oA = ADRP2+idx
            local idx_oB = idx_oA+1
            local oA, oB = peek4(idx_oA), peek4(idx_oB)

            if (oA & 1) == 1 then
                poke4( idx_A+GW-1 , peek4(idx_A+GW-1) + 2 )
                poke4( idx_A+GW   , peek4(idx_A+GW  ) + 2 )
                poke4( idx_A+GW+1 , peek4(idx_A+GW+1) + 2 )
                poke4( idx_A-1    , peek4(idx_A-1   ) + 2 )
                poke4( idx_A-GW-1 , peek4(idx_A-GW-1) + 2 )
                poke4( idx_A-GW   , peek4(idx_A-GW  ) + 2 )
                poke4( idx_A-GW+1 , peek4(idx_A-GW+1) + 2 )
            end
            if (oB & 1) == 1 then
                poke4( idx_B+GW-1 , peek4(idx_B+GW-1) + 2 )
                poke4( idx_B+GW   , peek4(idx_B+GW  ) + 2 )
                poke4( idx_B+GW+1 , peek4(idx_B+GW+1) + 2 )
                poke4( idx_B+1    , peek4(idx_B+1   ) + 2 )
                poke4( idx_B-GW-1 , peek4(idx_B-GW-1) + 2 )
                poke4( idx_B-GW   , peek4(idx_B-GW  ) + 2 )
                poke4( idx_B-GW+1 , peek4(idx_B-GW+1) + 2 )
            end
        end
    end
end

function next_gen()
    memcpy(ADRP, ADRC, (GW//2)*GH)

    for j=0, GH-1 do
        for i=0, GW-1, 2 do
            local idx_A = ADRC2+(i+j*GW)
            local idx_B = idx_A+1
            local A = peek4(idx_A)
            local B = peek4(idx_B)

            local idx_oA = ADRP2+(i+j*GW)
            local idx_oB = idx_oA+1
            local oA = peek4(idx_oA)
            local oB = peek4(idx_oB)

            -- cell A
            if oA ~= 0 then
                local nA = (oA >> 1) + (oB & 1)

                if (oA & 1) == 1 then
                    if ((nA ~= 2) and (nA ~= 3)) then
                        poke4(idx_A, A & ~1)

                        poke4( idx_A+GW-1 , peek4(idx_A+GW-1) - 2 )
                        poke4( idx_A+GW   , peek4(idx_A+GW  ) - 2 )
                        poke4( idx_A+GW+1 , peek4(idx_A+GW+1) - 2 )
                        poke4( idx_A-1    , peek4(idx_A-1   ) - 2 )
                        poke4( idx_A-GW-1 , peek4(idx_A-GW-1) - 2 )
                        poke4( idx_A-GW   , peek4(idx_A-GW  ) - 2 )
                        poke4( idx_A-GW+1 , peek4(idx_A-GW+1) - 2 )
                    end
                else
                    if (nA == 3) then
                        poke4(idx_A, A | 1)

                        poke4( idx_A+GW-1 , peek4(idx_A+GW-1) + 2 )
                        poke4( idx_A+GW   , peek4(idx_A+GW  ) + 2 )
                        poke4( idx_A+GW+1 , peek4(idx_A+GW+1) + 2 )
                        poke4( idx_A-1    , peek4(idx_A-1   ) + 2 )
                        poke4( idx_A-GW-1 , peek4(idx_A-GW-1) + 2 )
                        poke4( idx_A-GW   , peek4(idx_A-GW  ) + 2 )
                        poke4( idx_A-GW+1 , peek4(idx_A-GW+1) + 2 )
                    end
                end
            end

            -- cell B
            if oB ~= 0 then
                local nB = (oB >> 1) + (oA & 1)

                if (oB & 1) == 1 then
                    if ((nB ~= 2) and (nB ~= 3)) then
                        poke4(idx_B, B & ~1)

                        poke4( idx_B+GW-1 , peek4(idx_B+GW-1) - 2 )
                        poke4( idx_B+GW   , peek4(idx_B+GW  ) - 2 )
                        poke4( idx_B+GW+1 , peek4(idx_B+GW+1) - 2 )
                        poke4( idx_B+1    , peek4(idx_B+1   ) - 2 )
                        poke4( idx_B-GW-1 , peek4(idx_B-GW-1) - 2 )
                        poke4( idx_B-GW   , peek4(idx_B-GW  ) - 2 )
                        poke4( idx_B-GW+1 , peek4(idx_B-GW+1) - 2 )
                    end
                else
                    if (nB == 3) then
                        poke4(idx_B, B | 1)

                        poke4( idx_B+GW-1 , peek4(idx_B+GW-1) + 2 )
                        poke4( idx_B+GW   , peek4(idx_B+GW  ) + 2 )
                        poke4( idx_B+GW+1 , peek4(idx_B+GW+1) + 2 )
                        poke4( idx_B+1    , peek4(idx_B+1   ) + 2 )
                        poke4( idx_B-GW-1 , peek4(idx_B-GW-1) + 2 )
                        poke4( idx_B-GW   , peek4(idx_B-GW  ) + 2 )
                        poke4( idx_B-GW+1 , peek4(idx_B-GW+1) + 2 )
                    end
                end
            end
        end
    end
end


init()