The Combat Design of Signal Decay

Signal Decay is a tactical twin-stick shooter in stealth disguise. It is a distinct game with small numbers, that is, all the enemies’s health points and the count of them are small integers. It brings a distinct experience to the game. I would call it emergent problem-solving by teamwork. To enhance the co-op experience in game, Signal Decay emphasizes on tactics and de-emphasizes on long-term strategy to some degree. To describe it, it’s more like multiple players explore the map and get through a series of hard check-point with planning and reflex. The long-term strategy is supported by a dynamic alert level mechanic in game.

See the official wiki for specific designs.

Guard

Signal Decay has many kinds of enemies and traps. The compositions of them present emergent challenges to the players. The most common enemies are guards. Although guards have similar AI, they still become different challenges with different weapons and armors, which are countered by different player weapons and gadgets.

The core combat gameplay is shooting-from-behand – one player plays as a decoy to lure the guard, and the other can shoot him from behind. A guard has two armors in the front, so he can be killed by 3 shots from front and 1 shot from behind. When a player is found and faced by a guard, she becomes vulnerable and weak. Because the guard will be always faced to the player, which makes the player hard to fight against him. The player in this situation requires the help from the other player – a shot from behind. The co-op experience is all about caring about the other and nobody being left behind, instead of fighting as an individual without coordinations. The final result is the weaker player determines how far the team will go, similar to Heroes of the Storm, Overwatch (and Dota is the opposite).

A guard is stronger than an individual player. It requires two players to work together to eliminate a guard, and being chased makes a player desperate for the other’s help. This makes the gameplay in singleplayer mode so hard to be right. In singleplayer, once the player is being chased, there’s no teammate to help.

AI

The guards have the most complex AI to support the co-op experience. It is implemented by behavior trees. Guards’ AI states can be Idle, Suspect, Chase, Attack and Search and the transition states of them.

1. In Idle state the guard is overwatching or patrolling.
2. When a guard hears a small noise, he will turns to it.
3. When a guard sees a player or a decoy, he will be suspecting.
4. When a guard is suspecting for a while or receives an alarm event, he will turn on his radio, and start chasing at the players.
5. When a guard meets a player while chasing, he will attack.
6. When a guard can’t find any players in Chase state, he will start searching. In this state the guard will auto deduce where the player could be and search the floor.

To encourage the players to make an assault rather than lure everyone to a position with gun sounds. A special design is that when a guard is turning on his radio, he can’t attack at the same time. It takes quite some time. If the guard is lured by guns, when he meets the guard he will attack right away (because his radio was turned on when he started moving). This has a higher risk.

Weapons

Guards have different types of weapons:

• Assault Rifle: auto, low damage per shot
• Laser Rifle: manual, high damage per shot
• Shield and hand gun: low damage per shot, low fire rate, invincible from front. When the player is facing the guard, he will defend with the shield and shield bash the player; when the player is faced away, he will shoot the player.

Armors

• Regular front armor: blocks two damage. If the guard is dead without this armor broken, resources can be collected from the corpse
• Barrier: blocks damages from all directions. Prevent the guard from being tased or grabbed.

Counters

Signal Decay provides many types of weapons and gadgets to fight against enemies with different weapons and armors. The counters are mostly indirect.

Here are some examples:

• Melee weapons are not useful against sentry guns with gun shields.
• Taser can tase human enemies, but mechanical enemies are immune to it.
• Energy Converter and Stabilizer are effective to low damage weapons, and are not that useful to manual and high damage weapons.
• Active Barrier are effective to manual weapons on the contrary.
• Stabilizer makes a good loadout with Shotgun or Sniper Rifle.
• Guards with shields and some robots scanning nearby places are counters to Shotgun and Plasma Dagger and are countered by Rifle and area of effect weapon like Heat Rifle.

See wiki for more details