-- East slip kinks hard at segs 6,7,11,12 (27.8/17.5/58.2/50.1 deg). The slip
-- follows the mainline via centreAt(f), so either (a) the mainline bends
-- viciously at those samples, or (b) the slip's own path math misbehaves.
-- East runs join=551 -> land=539 (backwards, span=-12); west runs 525 -> 537.
-- Sample the mainline heading across BOTH spans to tell which.
local out = {}
local function say(s) table.insert(out, s) end

local map = workspace:FindFirstChild("Map")
if not map then return "Map MISSING" end

local deck = {}
for _, d in ipairs(map:GetDescendants()) do
	if d:IsA("BasePart") then
		local k = d.Name:match("^Road_(%d+)$") or d.Name:match("^Deck_(%d+)$")
			or d.Name:match("^RoadDeck_(%d+)$")
		if k then table.insert(deck, { i = tonumber(k), p = d.Position, cf = d.CFrame }) end
	end
end
table.sort(deck, function(a, b) return a.i < b.i end)
local byIdx = {}
for _, d in ipairs(deck) do byIdx[d.i] = d end
say(("mainline parts=%d idx %d..%d"):format(#deck, deck[1].i, deck[#deck].i))

local function report(lo, hi, label)
	say(("--- mainline heading, samples %d..%d (%s) ---"):format(lo, hi, label))
	local prev, acc = nil, 0
	local worst, worstAt = 0, -1
	for i = lo, hi do
		local d = byIdx[i]
		if d then
			local h = d.cf.LookVector
			if prev then
				local dth = math.deg(math.acos(math.clamp(prev:Dot(h), -1, 1)))
				acc += dth
				if dth > worst then worst = dth; worstAt = i end
				if dth > 4 then
					say(("   sample %d: turn %.1fdeg at (%.0f,%.0f,%.0f)"):format(i, dth, d.p.X, d.p.Y, d.p.Z))
				end
			end
			prev = h
		end
	end
	say(("   total=%.1fdeg  worst=%.1fdeg@%d"):format(acc, worst, worstAt))
end

report(525, 537, "WEST slip span - smooth one")
report(539, 551, "EAST slip span - ugly one")

-- Also: does the east span cross the sample-wrap boundary or reverse direction?
say("--- endpoint geometry ---")
for _, pair in ipairs({ { 525, 537, "west" }, { 551, 539, "east" } }) do
	local a, b = byIdx[pair[1]], byIdx[pair[2]]
	if a and b then
		local straight = (Vector3.new(a.p.X, 0, a.p.Z) - Vector3.new(b.p.X, 0, b.p.Z)).Magnitude
		say(("%s: join@%d=(%.0f,%.0f) land@%d=(%.0f,%.0f) straightDist=%.0f"):format(
			pair[3], pair[1], a.p.X, a.p.Z, pair[2], b.p.X, b.p.Z, straight))
	end
end

return table.concat(out, "\n")