Smart REM
Which Smart REM mode to use
Smart REM
Smart REM is the light inducer: Ludin flashes the screen red in bursts, aiming to put a recognisable signal into a dream you're already having. The only question is when to fire — and that's the difference between the two modes.
Do this after a WBTB wake, or with a midday nap. This tool is designed to be armed as you go back to sleep — either after a Wake-Back-to-Bed wake, or at the start of a midday nap. Sleep you re-enter that way reaches REM far sooner and holds it far longer than sleep you're just beginning, so the cue has real dream to land in. Armed at bedtime instead, it spends the first hours firing into non-REM sleep, where there's very little to become lucid inside.
That applies to both modes below. Sensor-Based can find REM without you telling it when, but it still can't create REM that isn't there — and the first hours of a normal night have very little of it.
Time-Based
You set a delay, and the flashes fire when it elapses. Ludin isn't measuring anything — you're timing REM yourself from cycle arithmetic, exactly the way the original light-flash induction devices worked. Predictable, transparent, and entirely dependent on your estimate being right.
Sensor-Based
Ludin monitors your phone's motion sensors while it lies on the mattress and works out when to fire for itself — then keeps monitoring and can fire again later in the same session. This is the part of Ludin that doesn't exist anywhere else, and the reason the app is worth having over a repeating alarm.
Set up Sensor-Based flashing →
So which one?
- Use Sensor-Based as your default. Timing is the whole problem light induction has always had, and estimating it beats guessing it.
- Use Time-Based when you want a known, repeatable variable — aiming a burst at a specific point into a nap or a post-WBTB sleep, or comparing the two modes against each other over a couple of weeks of journal entries.
Either way, the session shape is the same: WBTB wake or nap → arm one mode → back to sleep.
Photosensitivity. Both modes flash bright light repeatedly. If you have photosensitive epilepsy, or you're sensitive to flashing light for any reason, don't use them — the Timed Audio cue is an alternative that carries no flashing at all.
Both modes share the same burst controls — flash duration, gap between flashes, flashes per burst, repeat count and gap between repeats — but they ship with different defaults. Sensor-Based defaults to a longer, gentler, more spread-out cue, because it fires when it thinks you're in REM and can afford to. Don't assume a burst shape transfers between the two without checking.
One other difference: Time-Based fires its sequence and it's done. Sensor-Based keeps monitoring until you stop it, so a single arming can cue several REM periods across a session.