You have 5 hit points. You can wear a bit of armour, it protects against some types of attack. You can use a forcefield, it protects against some types of attack. On 0 hits you start dying, you're dead quite soon.
You can use swords (one-handed weapons), pistols, and laser pistols, and fire (but not load) crossbows. You can also use a sword and a pistol or laser pistol, or a dagger or buckler, but not ambidextrous swords or guns akimbo.
Melee combat is done using normal larp weapons. In order for attacks to be delivered past forcefields etc, the standard style which has developed is a slower, more graceful form of combat than is normally common. In practice, this means that all blows should be delivered slowly, without rapid tippy-tappy fighting. Only a touch is required to have a monoblade inflict serious injury, and so the art is in landing those touches. A good guideline is to keep your weapon close to the target for about half a second around calling your damage, instead of just flicking it in and whipping it out again immediately.
One-handed melee weapons all do single, as do polearms (while their reach is convenient, they have to be wielded with exceptional caution to ensure they don't bounce off forcefields). Two-handed weapons do double.
Ranged combat is point and shout with a 2s aiming period per call. Pistols have a range of 5m, rifles have a range of "as far as you can effectively shout". You are encouraged to use the aiming period to catch your target's eye and work out a good description so they know who you're shooting at.
Simple ranged weapons do double, and anyone may fire a crossbow. These shoot a projectile just slowly enough to bypass a forcefield, although as a consequence they fly quite slowly and may be easily dodged. Parrying an arrow is strictly forbidden on OC safety grounds.
Armour will give additional hits, and protects against melee weapons, simple ranged weapons, and laser weapons. However, gunpowder firearms bypass armour hits completely.
Shields and bucklers ignore all hits. Someone using a shield may also ignore ranged shots (but not laser shots) from people who are shooting from the rough quadrant in which the shield is carried - the guideline is basically "if you have the shield approximately between you and them, you're immune to their bullets", so think about front/side arcs etc as a way to get an idea. Note you can fight one person in melee while protecting yourself in another arc with your shield.
You have 5xp to spend on abilities.
One of the most signature items in Dune is the personal forcefield, which has basically obsoleted guns. The following rules are intended to give roughly this as an effect in play.
Wearing a forcefield requires a player to have illuminated shoulderpads or a similar item obviously on their person and lit up. While it is lit the forcefield is active - all players who can see this are IC aware of the forcefield being worn.
When a player with an active forcefield is shot by a gun, they take no effect at all from the bullet. When they are shot by a laser weapon, they must shout BACKLASH, see the next section. When they are struck in combat by a swift tappy blow, or struck by several blows in very swift succession, the forcefield will absorb all of these strikes as well.
A forcefield is, however, a bit picky. In particular, it is incompatible with a large shield, due to (technobabble), and no-one with a shield may use a forcefield. Obviously, users of forcefields also can't fire normal gunpowder weapons, as the bullets are caught on their way out and slowed down to an entirely harmless speed. Nor may they fire laser weapons - if they wish to do so they should call BACKLASH instead of making their damage call.
Backlash is the big downside for forcefields. When a LASER call is made at someone with an active forcefield, the target of that call should call BACKLASH. This is the cue for the person with the lasgun to also call BACKLASH. Backlash is essentially mass total, with all people within 5m immediately losing all hits. It's not pleasant, by a long way.
Dune! :D. Thinking about it, it's actually a kit-friendly system, since its classic old sci-fi the outfits range from high-medieval (Imperial court, Great Houses) -> silvered jumpsuits (Spacing Guild, Ix). I am somewhat puzzled as to why armour doesn't protect against gunpower weapons. --Drac