1.4b7 released!

SI 1.4b7 has been released! Click here to download the installer.

(Or click here if the installer gives you trouble)

Here is the list of changes:

  • New map si_caldera by grome
  • Crossbow
    • bow_alt svar added
    • When set, crossbow creates a Gravity Vortex on hit
    • This drags players back toward where they were hit
    • Tuning svars for this:
    • grav_range radius of the vortex (default 48 units)
    • grav_time how long the vortex lasts (default 0.25 seconds)
    • grav_rate how often the vortex drags (default 0.01 seconds)
    • grav_scale to scale up/down the drag based on distance (default 0.7)
  • Shotgun
    • Left and Right barrels now fire independently (firing one does not disable the other)
    • Primary attack is the left barrel, Secondary attack is the right barrel
    • Right barrel has a wider spread pattern - together, they form the same spread as the old doubleshot
    • Refire time of each barrel is 1.0 seconds
  • Flesh Eating Virus
    • Improved graphics
    • Slightly raised damage
  • Satchels no longer take damage (except from EMP)
  • Briefcase
    • Fixed swing animations
  • Tau Cannon now regenerates 1 ammo at a time
    • Still regenerates 3 ammo over 2 seconds
  • Bionic Muscle Fiber Enhancements and Exoskeleton Implants no longer raise scientist carry speed
  • Carry speed with a scientist is fixed (no matter how many your team has)
  • Removed heavy_alt testing svar
  • Spawn Protection removed
  • selfkill svar added (defaults to 0 - set to 1 to allow players to use the kill command)
  • Fixed issues with the HUD research completion notices and sounds
  • Fixed a crash when a scientist is thrown through a teleporter
  • General code quality pass (fixing lots of scary warnings)

1.4b6 released!

SI 1.4b6 has been released! Click here to download the installer.

(Or click here if the installer gives you trouble)

Here is the list of changes:

  • Tommygun
    • Fire rate reduced from 13/second to 9/second
    • Damage increased from 15 to 20
    • Reload time reduced from 2.1 to 1.2 seconds
    • Magazine size reduced from 50 to 30
  • Satchels
    • Added a 0.5 second arm time after landing, before they can be detonated
    • Can be destroyed by taking damage from explosions
  • Teleport kit
    • Primary fire: throw a teleport grenade OR detonate your active teleport grenade
  • GI Destabilizer
    • Primary fire: hitbox size reduced from 150 radius to 120
    • Bug fix: Secondary fire no longer pushes downed scientists through the map
  • Fixed a crash when players take damage from non-players
  • Briefcase
    • Reverted all recent changes
    • Should hit consistently as before
  • Cloning HUD restored on death
    • To show the full-screen map while respawning, use +showmap
  • Map updates
    • si_canyonero: new midfield bridge and entrances
    • si_hrim: scientists now use the short ramp in labs, lab medkit and battery moved to low lab entrance
  • LCS mode: Heavy armor, Radios and Mindray disabled

1.4b5 released!

SI 1.4b5 has been released! Click here to download the installer.

(Or click here if the installer gives you trouble)

Here is the list of changes:

  • Shotgun spread heavily revised

    • Primary fire now fires 9 pellets
    • Secondary fire now fires 17 pellets
    • Pellets deal 10 damage each (20 on headshot)
  • New implant: Heavy Armor

    • Available for research after Armor mk1
    • Takes 2 minutes to research
    • Reduces knockback from damage, taujumps and EMP jumps
    • Knockback is reduced by (your armor / your max armor)%
    • For example, if you have 150 out of 200 armor, the next hit does 75% less knockback
  • Bug fix: LCS mode no longer auto records each round as a separate demo

  • Flesh Eating Virus heavily revised

    • Primary fire throws a vial of Virus Type A
    • Secondary fire throws a vial of Virus Type B
    • A and B virus types can infect someone at the same time
    • Each vial has different looking clouds, and causes a different cough sound on hit
    • Adrenaline secondary fire has been removed
    • FEV infections now grow more predictably when standing in a cloud, or being hit with several clouds
  • All throwables now have the same speed/angle

    • Grenades, FEV, Radios, Satchels, Teleport grenades
    • Throw speed does not change based on your move speed
  • Quad visuals adjusted

    • All glow effects are team-coloured (not orange), and less intense than before
  • EMP on hit glow is now always white (not team-coloured)

    • Also less intense than before
  • Briefcase swing mechanics revised

    • Should be a bit more consistent than before, especially at higher ping

1.4b4 released!

SI 1.4b4 has been released! Click here to download the installer.

(Or click here if the installer gives you trouble)

Here is the list of changes:

  • New server settings to A/B test changes for the next patch:

    • hitreg_alt toggles between regular hitboxes (0) and static hitboxes that do not animate behind the scenes (1)
      • Players will still animate, but their hitboxes do not flail all over the place. Aim as you would normally!
    • grenade_alt toggles between normal grenades (0) and experimental grenades (1)
      • Experimental grenades do not inherit speed from the player. Secondary fire grenades are like primary fire, but not bouncy.
    • tripmine_alt toggles between normal tripmines (0) and experimental tripmines (1)
      • Experimental tripmines: secondary fire makes mines that aim at where you are standing, is unable to recall placed mines
  • Fixed Scientists going into the ‘carried’ animation while standing

  • New maps:

    • si_crucibleXL - A new take on si_crucible, suitable for larger playercounts
    • si_covfefe - suitable for small playercounts
    • lcs1 - A fun map to warm up in LCS mode
  • Updated maps:

    • si_carbon - Fixed some clipping issues


  • ie
  • guyonthecouch
  • parasite
  • grome
  • pears

1.4b3 released!

SI 1.4b3 has been released! Click here to download the installer.

(Or click here if the installer gives you trouble)

Here is the list of changes:

  • Ocular Implants

    • Your scientists now get the implant too!
    • Fixed graphics glitches, resets on death, flickering on high ping..
    • cl_oculars_intensity to adjust the visibility of blips (0 for invisible, 1.0 for fully visible)
    • Now shows players, scientists, radios, tripmines and satchels (does not show rockets, EMP pulses, nails..)
  • Shotgun secondary fire has a different spread

    • Same shape as primary fire, but wider with more pellets
    • Should be more consistent at most ranges
  • New map si_carbon

    • Based on the Quake 1 map dm3
    • Not yet finished, but getting close!
  • Added cl_quad_intensity to adjust the visibility of quad effects (0 for invisible, 1.0 for fully visible)

  • Added cl_gun_dlights to enable/disable dynamic lights on guns like tommygun (0 to disable, 1 to enable)

  • Reduced the number of models used by the game code

    • This means that we can play maps like si_replicant which have been unable to load since some of the earlier changes
  • New scientist models have team-coloured labcoats

  • EMP Cannon secondary fire kill icon fixed

  • Added the si_scisperside svar for experimentation

    • Default is 3 (scientists that spawn on each side at the start), 2 may be interesting with small playercounts


Click here to join the SI Discord server.

SI 1.4b2 released!

SI 1.4b2 has been released! Click here to download the installer.

(Or click here if the installer gives you trouble)

Here is the list of changes:

  • EMP Cannon secondary attack is the canister again
    • Lightning gun removed
  • Ocular Implants show markers for a bit more time after vision is lost

SI 1.4b1 released!

SI 1.4 has been released! Click here to download the installer.

(Or click here if the installer gives you trouble)

Here is the list of changes:

  • Redesigned Ocular Implants

    • Tier 3 implant: can be researched after exoskeleton, superjump, legs2 or ammo2 is complete
    • Reveals objects your teammates can see that are hidden from your view
    • Does not reveal cloaked enemies
    • Does reveal cloaked teammates
    • Research time is 1 minute
  • Restored the old Satchel firing speed (1 bomb / second)

  • New EMP Cannon secondary attack: Lightning gun!

    • Uses ammo at the same rate as primary fire
    • Each hit does 12 the damage of a primary fire pulse
    • Fires 13 times per second (same as tommygun)
    • Range is limited
    • Shocks a small area around where it hits (useful to destroy radios)
    • Shoot a flying EMP pulse to detonate it, discharging all ammo
  • New Teleport Kit models

  • New GI Destabilizer wave graphics

  • Rocket Pistol damage lowered to 110

  • Tau Cannon changes

    • Research time reduced to 2.5 minutes (from 3.25)
    • AOE nuke damage returned. Radius and damage are half of the main shot damage. Nukes happen on every wall pierced.
    • Charge time reduced from 1.7 seconds to 1.3 seconds
  • Updated the minimap sprites for resources, breakables, administrator, and dead players

  • Map update: si_crucible now a bit easier to defend thanks to new routes

  • Globally reduced knockback from damage by 40%

  • Dead players no longer drop items

    • Set the svar dropitems to 1 to restore the old behaviour
  • Added new commands to select weapons and devices more easily

    • weapon1 selects the pistol or briefcase (press again to cycle through items)
    • weapon2 selects shotgun or tommygun
    • weapon3 selects nailgun, hand grenades or FEV
    • weapon4 selects tau cannon, crossbow or rocket pistol
    • device1 selects cloak or radios
    • device2 selects mindray, EMP cannon or GI destabilizer
    • device3 selects tripmines, satchels or the teleport kit
    • This allows you to select all the weapons with a fixed set of 7 key binds
    • The only time you need to ‘double tap’ a key (to cycle items) is when you have multiple techs in the same group (e.g. tau and crossbow, mindray and EMP)
    • Other methods of selecting items are still available as before
  • Removed third person view (briefcase and cloak)

  • Updated the main menu

  • Updated the default config with better mouse, network and graphics settings

SI 1.3b8 released!

SI 1.3b8 has been released! Click here to download it.

Here is the list of changes:

  • Fixed Nailgun bleeding on players

  • Fixed Tau Cannon bugs

    • Kickback going in the wrong direction sometimes
    • Shots hitting the firing player sometimes
  • Added svars quadtime and quadrespawn to adjust quad damage resources

    • quadtime sets how long a picked-up quad lasts (default 20)
    • quadrespawn sets how long it takes a picked-up quad to respawn (default 60)
  • The teampanel will show teammates who have quad damage with an orange background

  • Kill notices from quad damage have an orange kill icon

  • Friendly fire kill notices show the weapon used

  • Restrict pitch and yaw adjustments (prevents rocketjump/taujump scripting)

  • Added the svar explosion_dropoff to change how explosions deal damage

    • Set this to 1 to make explosions smaller, but more damaging up close
    • Set this to 0 to have explosions behave as they used to
  • Removed a source of randomness in explosion damage

  • Added the hud_damageindicator cvar. Set this to 1 to disable the damage indicator sprite (or 0 to keep it on).

SI 1.3b7 Released!

SI 1.3b7 has been released. Click here to download it.

Here is the huge list of changes:

  • Map updates:

    • si_crucible: A new map full of Quake nostalgia, ideal for small teams.
    • si_late: Lots of revisions!
    • si_hrim: Lowered the middle of the mid-map, the elevators are now toggled by the buttons
    • si_mill: Lots of revisions! Scientists now only spawn on the bottom floor
    • si_vestibule: Lots of revisions! Trim on doorways, opened up the main lobby entrance
    • si_mesa: Added a map overview image and location markers
  • Added the Nailgun

    • Alternative to Grenades and FEV (tier 2 weapon)
    • Primary fire shoots nails that bounce with no friction (wide-angle reflections)
    • Secondary fire shoots nails that bounce with high friction, high gravity (tight-angle reflections)
    • Nails deal 80 damage
    • Fires 3 shots per second
    • Holds 5 shots, reloads in 1.5 seconds
    • Ideal for clearing out vents and tight hallways. Not so good in open areas.
    • Lots of svars to control these in testing:
      • ng_time: How long nails fly for before disintegrating (default is 0.8)
      • ng_grav: Gravity on secondary fire nails (default is 0.8)
      • ng_fric: Friction on secondary fire nails (default is 0.8)
      • ng_tt: How long the smoke trail draws for (default is 1)
      • ng_s: Size of nails, length of one side of the cube (s x s x s, default is 4)
  • Added Quad Damage

    • Replaces resources (when the svar quadresources is set to 1)
    • Lasts 20 seconds
    • Respawns in 1 minute. Does not spawn at game start.
    • All damage dealt by the player is multiplied by 4 while active
    • Official maps with resources: deep, daybreak, green, mercato, turf, overtime, spa…
    • A strategic powerup that lets one player stand out, clearing a path for their team
  • Tau Cannon changes:

    • No longer deals splash damage when hitting walls
    • Pierces walls, people and other objects over a large distance (set by the svar tau_distance, default is 8192)
    • Fixed fake shots when holstering the gun while charging
  • Mindray changes:

    • Simplified the sounds and visuals to be more reliable
    • Primary fire shoots 10 times per second, uses ammo quickly, has very long range and raises efficiency quickly
    • Secondary fire is unchanged
  • Crossbow damage raised from 120 to 125 (this actually matters)

  • Satchels are now thrown every 2 seconds (slowed from every 1 second)

  • Reduced the splash radius of rockets, grenades, satchels, teleport grenades

  • Reduced knockback from weapons globally (controlled by the svar dmg_kb, default is 4)

  • Added m_raw to control mouse settings.

    • Set this to 1 to get the same effect as the launch option -noforcemparms (no acceleration etc).
    • Set this to 0 and your mouse settings are unchanged.
    • If you had trouble recently with launch options or needed to run the rinput.exe tool, this should be just as effective (with less input lag and less moving parts).
  • The vote menu can be opened at any time. Your vote can be re-cast before the next tech starts researching.

  • Dead players are always indicated on the scoreboard (in all game modes)

  • Overview map now also shows resources, breakables and friendly living scientists

  • Health kits now add 50% of your maximum health when picked up

  • Armor kits now add 50% of your maximum armor when picked up

  • EMP bolts and grenades are now team-coloured

  • Improved consistency of wall jumping

  • Fixed zoom being stuck on while dead or spectating

  • Made radios and tripmines a bit easier to shoot

  • cl_autorecord now starts a new demo upon startmatch

    • No more searching in long demos for the game start time

1.3b6 Released!

SI 1.3b6 has been released. Here is the list of changes:

  • Map updates:

    • si_late: Lots of revisions!
    • si_hrim: A few small changes!
    • si_mill: Lots of revisions!
    • si_vestibule: A work-in-progress revision of si_alley
  • Research time changes:

    • Health regen 1 minute
    • Armor regen 1 minute
    • Tissue recycling 2 minutes
  • Scientist knockout and throw changes:

    • You can only knock out 1 scientist every 10 seconds
    • You can pick up and throw scientists (+attack2 with the briefcase) as often as you want
  • Zoom changes:

    • default_fov sets your regular FOV angle (e.g. 90 degrees)
    • zoom_fov sets your zoom FOV angle (e.g. 70 degrees)
    • Zooming is purely clientside
  • Crossbow refire time reduced to 0.75 seconds

    • Tracer effect removed
  • Many improvements to weapon switching delays

  • +use no longer slows down the player when pressed

  • FEV Secondary fire poison lasts 6 seconds (same as the adrenaline effect)

  • EMP can destroy teleport grenades. Teleport grenades cannot be killed otherwise.

  • Scientists thrown to the Administrator are captured automatically

  • Dead Scientists now use the player spawn times (4/3/2 seconds depending on Process tech)

  • Rocket Pistol barrel smoke effect removed

  • Fixed +attack being stuck on by the scoreboard

  • Added hud_saytext_volume to adjust the chat beep sound (1.0 is default, set to 0 for blissful silence)

  • Fixed lots of issues with the spectator view being broken

1.3b5 Changelog

  • Map updates:

    • si_bavaria: Made labs a bit easier to defend, improved the conveyer belts, lots of improvements to FPS
    • si_hrim: A very good new map by grome!
    • si_late: A different take on si_early, with changes to make gameplay faster and more interesting
  • Radios are brighter

  • EMP has a kill icon

  • LCS: dead players are shown with colorized names, instead of dead

  • Healthkits give 25 hp and Armor Batteries 25 armor

  • Mindray no longer reveals enemy research

  • Revised weapon switching:

    • If you hold +attack or +attack2 while selecting a weapon, you must release it before you can fire again
  • Fixed Superjump “head sliding”

  • Fixed Tau Cannon ‘wall bleeding’ on nukes

  • Tau Cannon can no longer shoot the sky

  • Disabled Ocular Implants.

  • Zoom is available by default, and there are no ranged damage upgrades.

  • Removed the saytext sound.

  • GI Destabilizer secondary fire pushes from lower

  • GI Destabilizer has instant deployment

  • Removed cl_effects_fev_cloud_density

  • Made consistency checking more strict: always checks all player and projectile models

  • Reduced FEV adrenaline time to 6 seconds

  • New cvars for weapon switching:

    • cl_altweapon_backup: set to 1 so you can equip an alt weapon without pushing +altweapon
    • cl_altweapon_cycling: set to 1 to enable cycling between a weapon and its alt without pushing +altweapon

Steam Group

Click here to visit the SI Steam Group.

Feel free to post on the forum about how much you love the game, or find out when the next pickup game will be played!


Click here to download the SI installer.

Or try here if the installer gives you trouble.

SI is a Half-Life mod. You need Half-Life installed to play it.

Extract the archive to your Half-Life directory in Steam.

When the mod is installed, your folder structure should look like this:

├── htmlcache
├── platform
├── si
├── valve
├── valve_hd


Here are some links to cool streams and videos of SI:

Official Channel: