Arm Arrives on Hydross Walkthrough

The Core Contingency opens with a hard sea battle. You start in the north-west corner of Hydross with a Commander, a Construction Ship, a Searcher scout ship, a Shark submarine killer and a Snake submarine. Arm has already built a base in the south-east. On Medium it has 149 units, among them three Millenium battleships, three Seaplane Platforms, two shipyards and 24 Sea Serpents, the planet's native life. You win only when every Arm unit and every Serpent is destroyed.

Nothing attacks you in the first two minutes, but from then on Arm's patrols cross the whole sea, and its Seaplane Platforms have orders for 260 Albatross seaplanes. Fortify your corner before the first Serpents arrive, build a fleet that out-ranges Arm's towers, and destroy the factories early. The rest can then be hunted down at leisure.

The Battlefield

Hydross is almost entirely sea. Your corner is dotted with shallows, and most of them carry a metal deposit. Arm's base sits on a large shallow bank around (5900, 5500), ringed with Defender - NS missile towers and Stingrays. Its Shipyard lies just north of the bank, its Seaplane Platforms east and south-east of it, and its Adv. Shipyard far to the south-west. Two walls of Floating Dragon's Teeth protect the base: one runs west of it from (5168, 6064) down to (4496, 7472), the other closes the east side from (6864, 4864) almost to the map edge.

Blue numbers mark the plan and red letters mark Arm. The map shows the Medium set-up.

Map of Arm Arrives on Hydross 1234567ABCDEFG
The planEnemy positionsYour unitsEnemy unitsHover a dot to see the unit and its orders. · Map 7,680 × 7,680 pixels · Scroll or pinch on the map to zoom; drag to move. Hover over a feature or a resource for its details.
  • 1Your start. Deposits worth 223 lie at (408, 360), (824, 248), (824, 552) and (632, 776), and one worth 127 at (936, 344).
  • 2The guard post. Four Sea Serpents turn round here, again and again, from 2:00 on.
  • 3Your Shipyard, between deposits at (888, 1064) and (1592, 776).
  • 4The fleet gathers here.
  • 5From here your Executioners shell Arm's Shipyard at A.
  • 6From here they shell the towers at the east end of the base: two Torpedo Launchers, two Defender - NS towers and the Stingrays behind them.
  • 7With those towers gone, sail round the west end of the eastern wall to here. All three Seaplane Platforms are then within 1300.
  • AArm's Shipyard. On Medium the nearest tower is more than 500 away.
  • BThree Seaplane Platforms, at (7184, 5872), (6976, 6512) and (7264, 6592).
  • CThe Underwater Fusion Plant, with a Colossus carrier at (6464, 5808). Both die in an atomic blast.
  • DThe Adv. Shipyard. From 15:00 it builds Conquerors, Rangers, Milleniums and Piranhas.
  • EThree Milleniums that wait until they are attacked, and the Advanced Sonar Station at (4512, 4272).
  • FFour Sea Serpents. From 2:00 they patrol to 2 and back.
  • GA Ranger and a Conqueror. At 21:40 and 23:20 they sail for your Shipyards.

Arm's Timetable

These are the Medium orders that matter, counted from the start of the mission. No Arm unit moves before 2:00.

Time What happens
2:00 The four Sea Serpents at F patrol to 2. A Lurker submarine at (3088, 2144) patrols to (1317, 3640).
3:20 Three Skeeters patrol from (6760, 3180) west to (392, 3570).
3:50 Five Sea Serpents in the north-east, near (6400, 650), patrol to (644, 3851).
5:00 Two Skeeters, at (6112, 5952) and (7472, 2784), attack your Construction Ships, then your Tidal Generators, Shipyards and Adv. Shipyards. Two Crusaders patrol from (2550, 6920) north to (3693, 964). Three Skeeters patrol from (4780, 2820) to about (2220, 4800).
6:40 Two Seaplane Platforms start their orders for Albatross. The third starts at 8:20.
8:20 Five Sea Serpents in the east, near (7360, 4080), patrol to about (530, 3135).
10:00 A Seahawk sonar plane patrols to (359, 187), over your start. Three Lurkers patrol from (5800, 3230) to (2947, 5912). The Shipyard starts its orders for Skeeters, Crusaders and Lurkers.
11:40 Six Sea Serpents in the south-west patrol to (6228, 3009). Four Skeeters attack your Construction Ships, Tidal Generators, Shipyards, Adv. Shipyards and Seaplane Platforms.
13:20 An Albatross patrols to (359, 187). A Piranha submarine patrols from (5920, 688) to (747, 5267).
15:00 Four Sea Serpents at (1700, 5970) patrol to the north-east near (6902, 1249). Two Lurkers patrol west and south-west from (6480, 2592) and (5744, 656). A Crusader patrols from (6736, 3440) to (3708, 6473). The Adv. Shipyard starts its orders.
21:40 The Ranger at G attacks your Shipyards, then your Adv. Shipyards, Seaplane Platforms and Torpedo Launchers.
23:20 The Conqueror at G attacks your Shipyards.
30:00 The Colossus patrols to (6746, 6510). An Arm Construction Ship patrols to (5409, 6982).
31:40 Three Albatross attack your Advanced Torpedo Launchers, Stingers, Hives, Torpedo Launchers and Construction Ships. A second Seahawk patrols to (322, 213).

The Plan on Medium

Make a Start (0:00 to 5:00)

  1. With the Commander, build Tidal Generators and Underwater Metal Extractors on the deposits at 1. The tidal strength is 26, and wind and solar plants are not allowed here.
  2. Send the Construction Ship to 2 and build a Thunderbolt there before 2:00. Its laser does 195 damage at a range of 410, and a Sea Serpent has 420 hit points and a flame thrower that reaches only 160. Park the Searcher, the Shark and the Snake behind it.
  3. Build a Shipyard at 3 with the Commander, then more Construction Ships and a few Enforcers. An Enforcer has 3150 hit points and a cannon with a range of 660.
  4. The two Skeeters that set off at 5:00 hunt Construction Ships first. Keep yours behind the Thunderbolt and the Enforcers.

Build Up (5:00 to 25:00)

  1. Before 10:00, put Stingers round 1. The Seahawk at 10:00 and an Albatross at 13:20 both patrol to (359, 187), right over your start, and an Albatross has only 216 hit points.
  2. Use a Construction Ship to build an Adv. Shipyard at 3. From it build an Advanced Construction Sub and a Hive. The sub builds an Underwater Fusion Plant and a Seaplane Platform.
  3. Build the fleet: Executioners and Missile Frigates, both with a range of 1300, two Shredders for anti-air, and two or three Leviathans.
  4. At 21:40 the Ranger leaves G for your Shipyards, and the Conqueror follows at 23:20. Meet them at sea, well before they come within 1300 of 3. The Ranger has only 1200 hit points. The Conqueror has 4050, but its depth charge reaches 410, and a Leviathan's torpedo does 812 damage from 500.

Strike the Factories (25:00 onward)

  1. Gather at 4 and sail to 5. Destroy the Shipyard at A from 1300.
  2. Move to 6 and destroy the Torpedo Launchers (range 400), the Defender - NS towers (700) and the Stingrays (480) at the east end of the base, all from 1300.
  3. Sail round the west end of the eastern wall at (6864, 4864). Kill the Defender - NS at (6480, 5024) and the Stingray at (6256, 5056) on the way. Then take the Advanced Torpedo Launcher at (7248, 5280), whose torpedoes reach 650, and the two towers at (6992, 5824) and (6992, 5904).
  4. From 7, destroy all three Seaplane Platforms. From then on Arm can only build at the Adv. Shipyard.
  5. Clear the bank from range. Shoot the Underwater Fusion Plant and the Colossus from well away, then go west for the Adv. Shipyard at D and the battleships at E.
  6. Hunt down the rest: every Sea Serpent, the Lurkers and Skeeters waiting near (3150, 6450), the Underwater Metal Extractors and the Tidal Generators at (6304, 6848) to (6576, 6944).

What Changes on Hard

  • Your forces and your starting 1000 metal and 1000 energy do not change.
  • Arm has 155 units instead of 149: 23 Defender - NS towers, 11 Stingrays, 4 Advanced Torpedo Launchers and 6 Underwater Metal Extractors. Two of the new towers, the new Advanced Torpedo Launcher and both new Stingrays stand right beside the Shipyard at A, at (6336, 4288) to (6416, 4448). Shell them from 5 before you touch the Shipyard.
  • The Conqueror comes for your Shipyards at 11:40 instead of 23:20, and the Ranger at 13:20 instead of 21:40.
  • All three Seaplane Platforms start almost at once. The one at (7184, 5872) orders 4 Albatross at 0:00 and 4 more every 1:40, the one at (7264, 6592) 3 every 1:40, and the one at (6976, 6512) 4 at 3:20. The Albatross patrol over your start begins at 11:40.
  • The Shipyard places all its orders at 6:40 and 13:20, and the Adv. Shipyard between 11:40 and 21:40. Then both stop.
  • A Lurker and a Crusader near (3100, 6500) finish waiting at 18:20 instead of 28:20 and 26:40.
  • The computer player keeps all the income its buildings make, against 70 percent on Medium.

Which Units Beat Theirs

Arm unit Its threat Your answer
Sea Serpent Fast (speed 5.8), 420 hit points, flame thrower at range 160 Thunderbolt (range 410) or Enforcer (660)
Skeeter Missiles of 31 damage at range 604, 560 hit points Enforcer or Thunderbolt
Lurker Submarine, torpedo of 350 at range 400 Depth charges of the Enforcer or Executioner, or a Leviathan (range 500)
Albatross Two torpedoes of 400 at range 300 Stinger (range 700), Shredder flak (146 damage, range 750)
Ranger Rocket of 500 damage at range 1300 Executioner (1300), or Leviathans that close in under water
Conqueror Cannon at range 1300, 4050 hit points Leviathans, from beyond its 410 depth charge
Millenium Two cannons of 260 at range 1250, 5720 hit points Executioners from 1300, or Titans (torpedo of 780)
Advanced Torpedo Launcher 1000 damage at range 650 Missile Frigate: two rockets of 500 kill one

Metal and Energy

The surface metal value is 3, so your metal comes from the 37 deposits, nearly all worth 223. Your corner has the best of them: besides the five at 1, there are deposits at (280, 984), (888, 1064), (1592, 776), (2088, 984), (680, 1640) and (1016, 1736). Claim them all before 10:00. Underwater Metal Storage holds 1500 metal.

Energy comes from the sea. The tidal strength is 26, and Tidal Generators cost only 81 metal and 752 energy. A Hive makes 380 energy and uses 45. The Underwater Fusion Plant makes 1200 and costs 7210 metal and 57,349 energy, so start it as soon as the Advanced Construction Sub is out.

Traps

  • The Underwater Fusion Plant at C and the Colossus beside it both die in an atomic blast of up to 2000 damage within 258 pixels. The Colossus starts to patrol at 30:00.
  • Attacking the Advanced Sonar Station at (4512, 4272) wakes three Albatross at (6000, 5380). They guard the station, then attack your Warlords, Snakes, Seaplane Platforms, Adv. Shipyards and Shipyards.
  • The battleships at E wake when they are attacked. The one at (4752, 4768) then patrols towards (2115, 2053), on your side of the map, and the one at (5328, 4560) goes for your Seaplane Platforms and Adv. Shipyards.
  • Arm's raids pick targets by type. The Skeeters at 5:00 and 11:40 go for Construction Ships first, the Ranger and the Conqueror for Shipyards, and the 31:40 Albatross for Advanced Torpedo Launchers and Stingers.
  • Your Commander is your best builder, and losing him loses the mission. Keep him at home under the Stingers.

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