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List of 1.7 levels :
TRAINING LEVEL : RL "Great Escape" - deleted prologue, go up to meet with Barneys, fight Xenians.
IMPOSSIBILITY DREAM : Intro/Tram Sequence (Secret : none)
BLACK MESA INBOUND : Get your suit (Secret : none)
ROUTINE WORK : Resonance Cascade occurs (Secret : Lost Battery : Get all batteries).
STATE OF EMERGENCY : Escape, find weapon(s) and allies (Secret : Demon Slayers : Find and clean up the vent).
LEGAL DEFENSE : HECU are in the place (Secret#1 : Circle of Death : Find alchemy circle, Secret#2 : Chaotic Butcher : Neutralize two fields of crabs).
ONE IS ALL, ALL IN ONE! : Bonus Level, only possible with Chaotic Butcher obtained, or mod played in Difficult setting (Secret : Dark Golden Energy : Get the Gravity gun in Surface Storage)
No secrets after this level.
GROUND ZERO : Lambda Reactor-like Level
BETWEEN WORLDS AND CHAOS : Xen-like level (Bonus Level, get all secrets in the previous levels).
NO WAY OUT : Surface Tension-like level
COUNTDOWN : Surface Tension-like level (#2)
ROUTE 2 "XEN" : save the scientist, get the door opened and run to the bomb :
NUCLEAR PORTAL : Weird mess between real world and Xen world.
RUINS OF CHRONOS : Xen level.
ASHES OF LAUTREC : Xen level + Combine-like installation.
If you find the "Talisman", then it's ALTAR OF SACRIFICE : final boss level.
If you don't find the "Talisman", you go back to Route 1 "HEART OF NIGHTMARE".
ROUTE 1 "BLACK MESA" : Jump in the "sewers"/tunnels instead of saving scientist :
ASHES TO ASHES, DUST TO DUST : tunnels/maze-like level.
HEART OF NIGHTMARE : Big battles in larges areas with giant crystals and radioactive stuff.
CENTER OF ALL THINGS : the final battle to stop the new alien race and the crystal processing, in Black Mesa.
THE SUN EATER'S PILLAR : Combine-like levels against countless waves of enemies, to finally stop the crystal processing.
AFTER ROUTE 1 AND 2 :
IMPOSSIBILITY DREAM (again) : Epilogue.
EPILOGUE : after credits. 4 maps and the "true" (?) ending.
Stay tuned for 1.8 version.