@LAZYGLOBAL OFF.

function any_flameout {
    //
    // Return true if any of our engines are starved for fuel. Primarily used to determine the need for staging.
    //
    local engines_list is LIST().
    list ENGINES in engines_list.
    for engine in engines_list {
        if engine:ignition and engine:flameout {
            return true.
        }
    }
    return false.
}


function should_stage {
    //
    // Return true if the rocket needs to stage.
    //
    return STATUS = "PRELAUNCH"  // e.g. still attached to launch tower
        or any_flameout()             // any engine starved for fuel
        or SHIP:maxthrustat(0) = 0.   // no active engines (e.g. when we have an intermediate stage for decouplers before activating the next engine)
}


function stage_when_ready {
    //
    // Stage when ready. Blocks until staging has been initiated.
    //
    wait until STAGE:ready.
    print "STAGING".
    STAGE.
}


function isp_sum {
    //
    // Return the sum of vacuum ISP for enabled engines.
    //
    local sum is 0.
    local engines_list is LIST().
    list ENGINES in engines_list.
    for engine in engines_list {
        if engine:ignition {
            set sum to sum + engine:vacuumisp.
        }
    }
    return sum.
}


function unlock_control {
    //
    // Ensure that the throttle is 0 and that the player is not locked out of control.
    //
    set SHIP:control:pilotmainthrottle to 0.
    set SHIP:control:neutralize to true.
    unlock STEERING.
    unlock THROTTLE.
}