Pico-1k: Doodle a Game!

poke(0x5f2d,1)
cnv_a={}
cnv_b={}
cnv_c={}
col=0
function _draw()
    lx,ly,mx,my,mb=mx,my,stat(32),stat(33),stat(34)~=0
    cls(7)camera()
    
    -- draw level
    canvas(cnv_b,1,1)
    canvas(cnv_a,1,1)
    
    -- playtest
    if play then
        ground=solid(px,py+1)
        dy+=0.4
        psx=lerp(psx,1,0.2)
        psy=lerp(psy,1,0.2)
        
        -- walking
        if btn(0) or btn(1) then
            if(btn(0))dx,flipx=max(dx-0.3,-2),1
            if(btn(1))dx,flipx=min(dx+0.3,2)
        else
            if ground then
                dx*=0.6
            end
        end
        
        -- jump
        if(ground and btn(4)) psx,psy,dy=.5,1.5,-5
        
        -- animation
        if(not wg and ground)psx,psy=1.25,.75
        wg=ground
        if(btn(3))psx,psy=lerp(psx,1.5,.3),lerp(psy,.5,.3)
        
        -- upsplope
        while solid(px+dx,py)
        and not solid(px+dx,py-2) do
            py-=1
        end
        
        -- horizontal
        if(solid(px+dx,py))dx=0
        px+=dx
        
        -- downslope
        if ground and
        not solid(px,py+1)
        and solid(px,py+4) do
            while not solid(px,py+1) do
                py+=1
            end
        end
        
        -- vertical
        if not solid(px,py)
        and solid(px,py+dy) do
            while not solid(px,py+sgn(dy)) do
                py+=sgn(dy)
            end
            dy=0
        end
        py+=dy
        
        -- draw player
        camera(-px,-py)
        canvas(cnv_c,psx,psy,flipx)
        
    -- draw elements
    else
        -- draw bg
        if state==1 then
            if(mb)add(cnv_b,{lx,ly,mx,my,6})
            if(btnp(4) or btnp(5))state=2
            ?"❎draw background",32,1,12
        -- draw player
        elseif state==2 then
            if(mb)add(cnv_c,{lx,ly,mx,my,0})
            canvas(cnv_c,1,1)
            if(btnp(4) or btnp(5))begin()
            ?"❎draw player",38,1,12
        -- draw level
        else
            if(mb)add(cnv_a,{lx,ly,mx,my,0})
            if(btnp(4) or btnp(5))state=1
            ?"❎draw level",40,1,12
        end
        line(mx,my,mx+3,my+3,0)
    end
end
-- utils
function begin()
dx,dy,psx,psy=0,0,1,1
px1,py1,px2,py2=256,256,0,0
for l in all(cnv_c) do
    px1=min(px1,min(l[1],l[3]))
    py1=min(py1,min(l[2],l[4]))
    px2=max(px2,max(l[1],l[3]))
    py2=max(py2,max(l[2],l[4]))
end
pw,ph=px2-px1,py2-py1
px,py=px1+pw/2,py1+ph
for l in all(cnv_c) do
    l[1]-=px1+pw/2
    l[3]-=px1+pw/2
    l[2]-=py1+ph
    l[4]-=py1+ph
end
play=1
end
function solid(px,py)
for x=-pw/4,pw/4 do
for y=-max(ph*.8,4),0 do
if(pget(px+x,py+y)==0)return 1
end end end
function canvas(t,sx,sy,f)
if(f)sx*=-1
for l in all(t) do
line(l[1]*sx,l[2]*sy,l[3]*sx,l[4]*sy,l[5])
end
end
function lerp(a,b,d)
return a+(b-a)*d
end