Graph.Edges(u@dir, v@dir) {
    ; if cost(v) = 0xff, we're off graph,
    ; in the padded area
    Graph.Edges := cost(v)
}

v@dir(u, dir) {
    v.dir := dir
    tmp := 1
    bt dir, 3
    if CF
        tmp := LINE_LEN
    bt dir, 2
    if CF
        tmp := -tmp
    v := u + tmp
}

neighbors(u@dir) {
    ; can always turn
    neighbors += v@dir(u, ~u.dir & 0b1000)
    neighbors += v@dir(u, (~u.dir & 0b1000) | 0b0100)
    ; can go forward if consec < 3
    if u.dir & 0b0011 < 3
        neighbors += v@dir(u, u.dir + 1)
}

; 12 possibilities, use 16 so we can do bit hacks
;      0000  0001  0010  0011  0100  0101  0110  0111   
;         0     1     2     3     4     5     6     7    
dir = {  R1,   R2,   R3,   XX,   L1,   L2,   L3,   XX,   
;      1000  1001  1010  1011  1100  1101  1110  1111
;         8     9    10    11    12    13    14    15  
         D1,   D2,   D3,   XX,   U1,   U2,   U3,   XX} 

dist[(x,y),dir]
prev[(x,y),dir]
   q[(x,y),dir]

for each vertex v in Graph.Vertices:
  dist[v] ← INFINITY
  prev[v] ← UNDEFINED
  add v to Q

for all real dir:
    dist[source@dir] ← 0

while Q is not empty and any dist[u] in Q < inf:
  u ← vertex in Q with min dist[u]
  remove u from Q
  for each neighbor v of u still in Q:
    alt ← dist[u] + Graph.Edges(u, v)
    if alt < dist[v]:
        dist[v] ← alt
        prev[v] ← u
done