-- Place: ServerScriptService.Checkpoints (Script)
local Players = game:GetService("Players")
local checkpoints = workspace:WaitForChild("Checkpoints")
local start = checkpoints:WaitForChild("Start")
assert(start:IsA("SpawnLocation"), "Checkpoints.Start must be a SpawnLocation")

local function initialize(player: Player)
    player:SetAttribute("CheckpointIndex", 0)
    player.RespawnLocation = start
end
Players.PlayerAdded:Connect(initialize)
for _, player in Players:GetPlayers() do initialize(player) end

for _, checkpoint in checkpoints:GetChildren() do
    if not checkpoint:IsA("SpawnLocation") then continue end
    local index = checkpoint:GetAttribute("Index")
    assert(typeof(index) == "number", checkpoint.Name .. " needs numeric Index")
    checkpoint.Touched:Connect(function(hit)
        local character = hit:FindFirstAncestorOfClass("Model")
        if not character then return end
        local player = Players:GetPlayerFromCharacter(character)
        local humanoid = character:FindFirstChildOfClass("Humanoid")
        local root = character:FindFirstChild("HumanoidRootPart")
        if not player or not humanoid or humanoid.Health <= 0 then return end
        if not root or not root:IsA("BasePart") then return end
        if not ((root.Position - checkpoint.Position).Magnitude <= 10) then return end
        local previous = player:GetAttribute("CheckpointIndex") or 0
        if index <= previous then return end
        player:SetAttribute("CheckpointIndex", index)
        player.RespawnLocation = checkpoint
        print(player.Name, "reached checkpoint", index)
    end)
end