【进阶实战】后跳闪避：向后位移的无敌帧封装

local CD = 8
local function backStep(actor)
    local last = tonumber(getplayvar(actor, 0, "BackLast")) or 0
    if os.time() - last < CD then
        sendmsg(actor, 1, "后跳冷却中，剩 " .. (CD - (os.time() - last)) .. " 秒。")
        return
    end
    setplayvar(actor, 0, "BackLast", os.time(), 0)
    setplayvar(actor, 0, "InvUntil", os.time() + 1, 0)
    sendmsg(actor, 1, "后跳！0.5 秒无敌帧。")
end

local function isInvincible(actor)
    local untilTs = tonumber(getplayvar(actor, 0, "InvUntil")) or 0
    return os.time() < untilTs
end