Terrain Reachability
TSQL query, 205 191 bytes
Input is a table variable @t
@x=start xpos, @y=start ypos
@i=end xpos  , @j=end ypos
@ =speed
DECLARE @t table(x int,y int,v int)
INSERT @t
values
(0,0,1),(0,1,1),(0,2,2),(0,3,1),(0,4,null),
(1,0,1),(1,1,2),(1,2,2),(1,3,1),(1,4,1),
(2,0,2),(2,1,1),(2,2,1),(2,3,2),(2,4,1),
(3,0,null),(2,1,null),(2,2,null),(2,3,1),(2,4,2)

DECLARE @x INT=2,@y INT=3,@i INT=0,@j INT=1,@ INT=5;

WITH C as(SELECT @y f,@x r,@ s
UNION ALL
SELECT f+a,r+b,s-v FROM C
JOIN(values(1,0),(0,1),(-1,0),(0,-1))x(a,b)ON
s&gt;0JOIN @t
ON f+a=x and r+b=y)SELECT
max(iif(S&gt;=0and f=@j and r=@i,1,0))FROM c

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