In most cases, I put 7 turrets in the bottom layer, 1 turret in the middle layer.

Summary of test results by rating
6 Shotgun + 2 Light Blade - Rating 9.1
8 Shotgun - Rating 8.5
6 Grenade + 2 Light Blade - Rating 8.2
8 Grenade - Rating 7.7
8 GUN 311 - Rating 7.2
7 Shotgun + 1 Turret Beacon - Rating 7.2
6 Light Blade + 2 Shield - Rating 7.0
5 Railgun + 3 Light Blade - Rating 6.3
6 Light Blade + 2 Laser - Rating 6.3
6 Light Blade + 2 Slowing Laser - Rating 6.2
6 Light Blade + 2 Gun 311 - Rating 6.2
6 Light Blade + 2 Weakening Laser - Rating 6
8 Drone (1:7) - Rating 6
8 Railgun - Rating 6
5 Shotgun + 3 GUN 311 - Rating 6.6
8 Machine Gun - Rating 5.1
4 Light Blade + 4 Laser - Rating 5.2
8 Drone (4:4) - Rating 4.3
5 Light Blade, 3 Teleport - Rating 4
8 Fury - Rating 3.5

Evaluation
Based on the bottom layer test results, Shotgun, Grenade, Light Blade stand out as some of the strongest options. However, since this is only a bottom layer test, their effectiveness in real situations with more turrets in other layers may vary.

A Teleport Turret can create a never-ending night by indefinitely teleporting the last enemy up, allowing for indefinite night mining. However, this requires considerable micromanagement and skill. Additionally, Repair Stations function at night, enabling unlimited repairs, though the process is very slow.

Synergy turret is usually beneficial when it can connect to 3 or more other turrets.

Slowing Laser and Weakening Laser, don’t seem very effective in the bottom layer tests, but they can be effective in other situations. In a boss fight, Slowing Laser is very helpful.

Test Conditions
- Number of turrets: 8. Mostly in the bottom layer.
- Difficulty: Ten
- Planet: Cavernous
- Platform: Earthcrusher (Level 15, fully unlocked)
- Core: None
- Bonus Perks:
+1 turret slot
-1 building price
- Defensive Setup:
1 Guard troop
No turret upgrades during the mission
No additional defense systems
No player control
- Depth: 100 m (drilled down only once)
- Tech Trees: Fully unlocked

Ratings
My ratings reflect my estimation of the effectiveness of each turret configuration, taking into account how many nights it can endure, as well as the remaining HP and enemies.
For example, if the core is destroyed in 7th night, the rating is 6 or more.
Build cost is not considered.

Note
Mission conditions, including bonuses and handicaps, vary randomly for each mission.
I wasn’t aware of this when conducting the bottom layer test, so the results and turret evaluations might be inaccurate in some parts.

Tools
WeMod, a game memory editing tool, was used to easily obtain resources for building.

8 Drone (1:7)
Middle layer: 1 Drone
Bottom layer: 7 Drone
Night 4: 89 % remained
Night 5: 56 % remained
Night 6: 11 % remained
Night 7: Core destroyed
Rating: 6/10

8 Drone (4:4)
Middle layer: 4 Drone
Bottom layer: 4 Drone
Night 4: 30 % remained
Night 5: Core destroyed
Rating: 4.3/10
Note: Placing many Drone turrets in the bottom layer is more effective than in middle layer.
Likely because enemies stay in the bottom layer for a long time, keeping the turrets closer to their targets.

4 Light Blade + 4 Laser
Middle layer: 4 Light Blade
Bottom layer: 4 Laser
Night 4: 70 % remained
Night 5: 34 % remained
Night 6: Core destroyed
Rating: 5.3/10

6 Light Blade + 2 Laser
Middle layer: 1 Light Blade
Bottom layer: 5 Light Blade, 2 Laser
Night 4: 85 % remained
Night 5: 64 % remained
Night 6: 39 % remained
Night 7: Core destroyed
Rating: 6.3/10
Note: Light Blade is strongest when positioned at the second-lowest slot in the bottom layer.
Laser turrets can also attack underground enemies during the daytime, making them a good addition.

6 Light Blade + 2 Gun 311
Middle layer: 1 Light Blade
Bottom layer: 5 Light Blade, 2 Gun 311
Night 4: 81 % remained
Night 5: 56 % remained
Night 6: 27 % remained
Night 7: Core destroyed
Rating: 6.2/10

6 Light Blade + 2 Shield
Middle layer: 2 Light Blade, 1 Shield
Bottom layer: 4 Light Blade, 1 Shield
Night 4: 86 % remained
Night 5: 72 % remained
Night 6: 57 % remained
Night 7: 22 % remained
Night 8: Core destroyed
Rating: 7.2/10
Note: A Shield turret halts enemies until it loses its power, allowing Light Blade turrets to inflict more damage.
For example, if a Shield turret is positioned in the 4th slot, the Light Blade turret should be placed in the 2nd slot, or 1st slot.
This combination may not be very effective for boss fight.

5 Light Blade + 3 Teleport
Middle layer: 1 Light Blade
Bottom layer: 4 Light Blade, 3 Teleport
Night 4: 15 % remained
Night 5: Core destroyed
Rating: 4/10
Note: Replacing three Light Blade turrets with three Teleport turrets does not appear to be beneficial. However, placing a single Teleport turret at the topmost position can effectively extend the night indefinitely by continuously sending the last enemy upward—provided there are no long-range turrets, such as Lasers, nearby. This strategy can be particularly useful for night mining.

6 Light Blade + 2 Weakening Laser
Middle layer: 1 Light Blade
Bottom layer: 5 Light Blade, 2 Weakening Laser
Night 4: 83 % remained
Night 5: 58 % remained
Night 6: 6 % remained
Night 7: Core destroyed
Rating: 6/10

8 Railgun
Middle layer: 1 Railgun
Bottom layer: 7 Railgun
Night 4: 68 % remained
Night 5: 39 % remained
Night 6: 3 % remained
Night 7: Core destroyed
Rating: 6/10

5 Railgun + 3 Light Blade
Middle layer: 1 Railgun
Bottom layer: 4 Railgun, 3 Light Blade
Night 4: 81 % remained
Night 5: 62 % remained
Night 6: 38 % remained
Night 7: Core destroyed
Rating: 6.3/10

6 Light Blade + 2 Slowing Laser
Middle layer: 1 Light Blade
Bottom layer: 5 Light Blade, 2 Slowing Laser
Night 4: 82 % remained
Night 5: 63 % remained
Night 6: 34 % remained
Night 7: Core destroyed
Rating: 6.2/10
Note: Slowing Laser turrets slow down enemies, allowing Light Blade turrets to deal more damage.

8 Grenade
Middle layer: 1 Grenade
Bottom layer: 7 Grenade
First Test
Night 4: 81 % remained
Night 5: 72 % remained
Night 6: 52 % remained
Night 7: 23 % remained
Night 8: Core destroyed
Rating: 7.2
Second Test
Night 4: 86 % remained
Night 5: 75 % remained
Night 6: 51 % remained
Night 7: 23 % remained
Night 8: 9 % remained
Night 9: Core destroyed. 19 or more big enemies remained.
Rating: 8.1
Average Rating: 7.7
Note: The Grenade is relatively inexpensive, requiring only 2 blue stones and 2 red stones, and is very powerful. In my other test, Grenade against the boss is fairly effective, but not the best.

6 Grenade, 2 Light Blade
Middle layer: 2 Grenade
Bottom layer: 4 Grenade, 2 Light Blade
First Test
Night 4: 89 % remained
Night 5: 77 % remained
Night 6: 70 % remained
Night 7: 40 % remained
Night 8: 5 % remained
Night 9: Core destroyed
Rating: 8/10
Second Test
Night 4: 93 % remained
Night 5: 85 % remained
Night 6: 69 % remained
Night 7: 50 % remained
Night 8: 20 % remained
Night 9: Core destroyed. 16 or more big enemies remained.
Rating: 8.3
Rating: 8.2
Note: The most effective setup among the 8 turret tests. However, this combination is not very effective against the boss.

8 Fury
Bottom 7 Fury,
Night 2: 72 % remained
Night 3: 39 % remained
Night 4: Core destroyed. 8 big enemies remained.
Rating: 3.5

8 Shotgun
Night 4: 94 % remained
Night 5: 82 % remained
Night 6: 72 % remained
Night 7: 48 % remained
Night 8: 26 % remained
Night 9: Core destroyed. 12 big enemies remained.
Rating: 8.5

8 Machine Gun
Night 3: 88 % remained
Night 4: 47 % remained
Night 5: 7 % remained
Night 6: Core destroyed. 21 big enemies remained.
Rating: 5.1

8 GUN 311
Night 3: 82 % remained
Night 4: 67 % remained
Night 5: 60 % remained
Night 6: 50 % remained
Night 7: 9 % remained
Night 8: Core destroyed. 18 big enemies remained.
Rating: 7.2

5 Shotgun + 3 GUN 311
Night 4: 98 % remained
Night 5: 78 % remained
Night 6: 47 % remained
Night 7: Core destroyed. 10 big enemies remained.
Rating: 6.6

6 Shotgun + 2 Light Blade
Night 4: 91 % remained
Night 5: 87 % remained
Night 6: 80 % remained
Night 7: 60 % remained
Night 8: 42 % remained
Night 9: 14 % remained
Night 10: Core destroyed. Boss 1st attack. Boss 90% HP remained.
Rating: 9.1

7 Shotgun + 1 Turret Beacon
A Turret Beacon is not a turret, but it increases all turrets attack range by 7 %.
Night 6: 47 % remained
Night 7: 13 % remained
Night 8: Core destroyed. 17 big enemies remained.
Rating: 7.2
Note: 1 Turret Becon instead of 1 Shotgun decreased the defence power.

Conditions
Depth: 150 m (Drilled down twice)
Bottom layer has base defence: 5 Machin Gun, 2 GUN 311, 1 Guard troop
I tested various type of turrets by putting 7 of them in the top layer, most of the time.
FYI, the core's max HP is 3800.
Other conditions are mostly the same with the bottom layer (8 Turrets) test.

Summary of test result by rating
7 Fury - Rating 8.8
5 Fury, 2 Weakening Laser - Rating 7.8
7 Shotgun - Rating 7.6
5 Fury, 2 Slowing Laser - Rating 7.5
7 Drone - Rating 7.4
3 Automatic, 4 Poison - Rating 7.3
7 Automatic - Rating 7
7 Grenade - Rating 6.7
7 Minigun - Rating 6.6
7 Poision - Rating 6.6
7 Mines - Rating 6.6
5 Machine Gun, 2 Weakening Laser - Rating 6.6
5 Machine Gun, 2 Slowing Laser - Rating 6.5
7 Machine Gun - Rating 6.4
4 Light Blade, 3 Slowing Laser - Rating 6.3
7 Mortar - Rating 6.2
7 Railgun - Rating 6.2
7 Fireworks - Rating 6.2
7 Rocket - Rating 5.6
7 Light Blade - Rating 5.6

Evaluation
Fury turrets seem to be the strongest choice for the top layer, as they can attack multiple enemies simultaneously.

Shotgun, Drone, Automatic, and Poison turrets are also highly effective.

Utility turrets like Weakening Laser and Slowing Laser can also be valuable depending on the configuration.

Light Blade and Grenade turrets are powerful turrets in the bottom layer but they don't seem to be as effective in the top layer.

Note: Left/Right Side Deployment
Mid-range turrets (around 12 blocks like Minigun or Poison turrets) and short-range turrets perform best when there is an equal distribution of slots on both the left and right sides.
However, if there is a significant imbalance in the number of slots on either side, a Synergy turret can compensate for the reduced effectiveness of the defense caused by this asymmetry.

In these tests, Synergy turrets were not used. I attempted to position the turrets symmetrically on the left and right sides, although this was not always achieved.

Top layer: 7 Machine Gun
Night 5: 72 % remained
Night 6: 25 % remained
Night 7: Core destroyed. 13 or more big enemies remained.
Rating: 6.4

Top layer: 7 Light Blade
Night 5: 57 % remained
Night 6: Core destroyed
Rating: 5.6
Note: Filling all 7 slots with Light Blade in the top layer doen't seem very effective choice.

Top layer: 4 Light Blade, 3 Slowing Laser
Night 5: 80 % remained
Night 6: 38 % remained
Night 7: Core destroyed. 16 big enemies remained.
Rating: 6.3
Note: Slowing Laser turrets reduce enemy speed, enforcing them to stay longer within the damage zone of the Light Blade turrets.

Top layer: 7 Grenade
Night 5: 100 % remained
Night 6: 62 % remained
Night 7: Core destroyed
Rating: 6.7
Note: Relatively cheap, yet effective.

Top layer: 7 Railgun
Night 5: 100 % remained
Night 6: 19 % remained
Night 7: Core destroyed
Rating: 6.2

Top layer: 7 Minigun
Night 5: 97 % remained
Night 6: 75 % remained
Night 7: Core destroyed
Rating: 6.6

Top layer: 7 Drone
Night 5: 86 % remained
Night 6: 83 % remained
Night 7: 32 % remained
Night 8: Core destroyed
Rating: 7.4
Note: Drone turrets in the top layer are far from the bottom layer, but drones still reach the bottom, shoot once or twice, and blow up. This would help a little in the boss fight.

Top layer: 7 Automatic
Night 5: 77 % remained
Night 6: 73 % remained
Night 7: 1 % remained
Night 8: Core destroyed
Rating: 7
Note: Automatic turrets deal much more damage to enemies with HP above 60%, but they are less effective against enemies with lower HP. Deploying seven Automatic turrets in the top layer might be excessive.

Top layer: 7 Poison
First test
Night 5: 73 % remained
Night 6: 53 % remained
Night 7: Core destroyed, 5 big enemies remained.
Rating: 6.8
Second test
Night 5: 81 % remained
Night 6: 30 % remained
Night 7: Core destroyed, 11 big enemies remained.
Rating: 6.4
Average rating: 6.6
Note: Poison turrets deal damage over a few seconds, but their effect wears off by the center of the middle layer. While multiple poison hits can quickly drain enemies' HP, their effectiveness might be slightly reduced if the middle layer is fully equipped with turrets, as some enemies may die before taking the full damage from the poison.

Top layer: 3 Automatic, 4 Poison
First test (Left: 1 Poison, Right: 3 Automatic, 3 Poison)
Night 5: 62 % remained
Night 6: 9 % remained
Night 7: Core destroyed.
Rating: 6.1
Second test (Left: 1 Automatic, Right: 2 Automatic, 4 Poison)
Night 5: 90 % remained
Night 6: 84 % remained
Night 7: 53 % remained
Night 8: 31 % remained
Night 9: Core destroyed. 11 big enemies remained.
Rating: 8.4
Average rating: 7.3
Note: A balanced deployment of Automatic turrets on the left and right appears to perform better than a balanced placement of Poison turrets.

Top layer: 7 Fireworks
Left: 1, Right 6
Night 5: 66 % remained
Night 6: 12 % remained
Night 7: Core destroyed. 15 or more big enemies remained.
Rating: 6.2
Note: If there had been balanced slots on the left and right sides, the results would have been better.

Top layer: 7 Mortar
Night 5: 78 % remained
Night 6: 13 % remained
Night 7: Core destroyed. 15 or more big enemies remained.
Rating: 6.2

Top layer: 7 Shotgun
Night 5: 100 % remained
Night 6: 87 % remained
Night 7: 52 % remained
Night 8: Core destroyed. 8 big enemies remained.
Rating: 7.6

Top layer: 7 Rocket
Night 5: 68 % remained
Night 6: Core destroyed. 8 big enemies remained.
Rating: 5.6

Top layer: 7 Mines
Night 5: 95 % remained
Night 6: 82 % remained
Night 7: Core destroyed. 8 big enemies remained.
Rating: 6.6

Top layer: 7 Fury
Night 5: 96 % remained
Night 6: 89 % remained
Night 7: 68 % remained
Night 8: 37 % remained
Night 9: Core destroyed. 5 big enemies remained.
Rating: 8.8
Note: Area attack that burns all enemies within its line of fire. Strongest turret I've tested.

Top layer: 5 Fury, 2 Weakening Laser
Night 5: 91 % remained
Night 6: 77 % remained
Night 7: 57 % remained
Night 8: Core destroyed. 5 big enemies remained.
Rating: 7.8
Note: Given that the rating of all 7 Fury turrets is 9.8, replacing 2 of them

Top layer: 5 Fury, 2 Slowing Laser
Night 5: 75 % remained
Night 6: 62 % remained
Night 7: 37 % remained
Night 8: Core destroyed. 11 big enemies remained.
Rating: 7.5
Note: Similarily with Weakening Laser turret, replacing 2 Fury turrets with Slowing Laser turrets doesn't seem to provide much synergy.

5 Machine Gun, 2 Weakening Laser
Top layer: 1 Weakening Laser, 2 Machine Gun
Middle layer: 1 Weakening Laser, 3 Machine Gun
Night 5: 83 % remained
Night 6: 53 % remained
Night 7: Core destroyed. 9 big enemies remained.
Rating: 6.6
Note: Considering the rate of all 7 Machine Guns is 7.4, it might be better to replace one or two of them with Weakening Lasers.

5 Machine Gun, 2 Slowing Laser
Top layer: 1 Slowing Laser, 2 Machine Gun
Middle layer: 1 Slowing Laser, 3 Machine Gun
Night 5: 67 % remained
Night 6: 47 % remained
Night 7: Core destroyed. 12 big enemies remained.
Rating: 6.5
Note: Considering the rate of all 7 Machine Guns is 7.4, it might be better to replace one or two of them with Slowing Lasers.

Test settings
Depth: 150 m (Drilled down twice)
1 Guard troop
The full 21 turrets are equipped across the top, middle, and bottom layers.

Full 3 Layers Test Summary by Rating
18 Fury + 3 Synergy - Rating 13.5
13 Fury + 3 Synergy + 3 Weakening + 2 GUN 311 - Rating 13.5
21 Fury - Rating 11.5
15 Fury + 9 Poison - Rating 10.9
17 Fury + 3 Synergy + 1 Shield - Rating 10.8
14 Fury + 7 Railgun - Rating 10.5
7 Fury, 7 Fury, 7 Shotgun - Rating 10.3
21 Shotgun - Rating 9.7
14 Fury + 7 Drone - Average Rating 9.5
14 Fury + 7 Grenade - Rating 9.5
14 Fury + 7 Laser - Rating 9.4
14 Fury + 7 GUN 311 - Rating 8.9
14 Poison + 7 Laser - Rating 8.3
21 Drone - Rating 7.3
14 Automatic + 7 Laser - Rating 6.9

Note: Ratings can vary from test to test, especially depending on the night the boss appears, so they may not be very accurate.
Slowing Laser and Light Blade turrets can be also useful (not tested here though).

7 Fury, 7 Fury, 7 Fury
First Test
Night 8: 80 % remained
Night 9: 56 % remained. Boss 1st attack.
Night 10: 45 % remained
Night 11: 32 % remained
Night 12: Core destroyed. Boss 2nd attack. The boss HP 12% remained.
Rating: 11.8
Second Test
Night 10: 56 % remained
Night 11: 7 % remained. Boss 1st attack.
Night 12: Core destroyed. 18 big enemies remained.
Rating: 11.2
Average Rating: 11.5

18 Fury + 3 Synergy
6 Fury + 1 Synergy, 6 Fury + 1 Synergy, 6 Fury + 1 Synergy
Night 5: 93 % remained
Night 6: 92 % remained
Night 7: 90 % remained
Night 8: 85 % remained
Night 9: 75 % remained
Night 10: 69 % remained
Night 11: 28 % remained. Boss 1st attack.
(The boss is manually targeted)
Night 12: 14 % remained
Night 13: 3 % remained
Night 14: Core destroyed. Boss 2nd attack. The boss HP 25% remained.
Rating: 13.5

14 Fury + 3 Synergy + 3 Weaking + 2 GUN 311
5 Fury + 1 Synergy + 1 Weakning, 
5 Fury + 1 Synergy + 1 Weakning, 
3 Fury + 1 Synergy + 1 Weakning + 2 GUN 311
Night 5: 99 % remained
Night 6: 97 % remained
Night 7: 96 % remained
Night 8: 94 % remained
Night 9: 72 % remained
Night 10: 66 % remained
Night 11: 16 % remained. Boss 1st attack.
(The boss is manually targeted)
Night 12: 11 % remained
Night 13: 5 % remained
Night 14: Core destroyed. 14 or more big enemies remained.
Rating: 13.5
Note: I used Weakening and GUN 311 to prepare for the boss fight, but they seem to lower the defence power instead.

7 Drone, 7 Drone, 7 Drone
Night 6: 100 % remained
Night 7: 22 % remained
Night 8: Core destroyed. 15 big enemies remained.
Rating: 7.3

7 Fury, 7 Fury, 7 Drone
1st Test
Night 8: 100 % remained
Night 9: 74 % remained
Night 10: Core destroyed. Boss 1st attack. The boss HP 85% remained.
Rating: 9.3
2nd Test
Night 8: 95 % remained
Night 9: 74 % remained
Night 10: Core destroyed. Boss 1st attack. The boss HP 80% remained.
(The boss is manually targeted)
Rating: 9.6
Average Rating: 9.5 (or less depending on boss apprearance)

7 Fury, 7 Fury, 7 GUN 311
1st Test
Night 7: 99 % remained
Night 8: 95 % remained
Night 9: Core destroyed. Boss 1st attack. The boss HP 82% remained.
Rating: 8.4
2nd Test
Night 7: 93 % remained
Night 8: 93 % remained
Night 8: 85 % remained
Night 9: 76 % remained
Night 10: Core destroyed. Boss 1st attack. The boss HP 80% remained.
(The boss is manually targeted)
Rating: 9.4
Average Rating: 8.9 (or less depending on boss apprearance)

7 Shotgun, 7 Shotgun, 7 Shotgun
Night 6: 96 % remained
Night 7: 94 % remained
Night 8: 90 % remained
Night 9: 83 % remained
Night 10: Core destroyed. Boss 1st attack. The boss HP 65% remained.
(The boss is manually targeted)
Rating: 9.7 (or less depending on boss apprearance)

7 Fury, 7 Fury, 7 Grenade
Night 9: 87 % remained
Night 10: Core destroyed. Boss 1st attack. The boss HP 77% remained.
(The boss is manually targeted)
Rating: 9.5 (or less depending on boss apprearance)

7 Fury, 7 Fury, 7 Railgun
Night 9: 58 % remained
Night 10: 45 % remained
Night 11: Core destroyed. Boss 1st attack. The boss HP 82% remained.
(The boss is manually targeted)
Rating: 10.5 (or less depending on boss apprearance)

7 Fury, 7 Fury, 7 Laser
Night 9: 60 % remained
Night 10: Core destroyed. Boss 1st attack. The boss HP 88% remained.
(The boss is manually targeted)
Rating: 9.4 (or less depending on boss apprearance)

7 Poison, 7 Poison, 7 Laser
Night 8: 92 % remained
Night 9: Core destroyed. Boss 1st attack. The boss HP 92% remained.
(The boss is manually targeted)
Rating: 8.3

14 Automatic, 7 Laser
7 Automatic,
4 Automatic + 3 Laser,
3 Automatic + 4 Laser  
Night 6: 98 % remained
Night 7: Core destroyed. 1 big enemies remained.
Rating: 6.9

7 Fury, 7 Fury, 7 Shotgun
Night 10: 72 % remained
Night 11: Core destroyed. Boss 1st attack. Boss 70% HP remained.
Rating: 10.3

15 Fury + 9 Poison
Each layer has 5 Fury + 3 Poison
Night 10: 64 % remained
Night 11: Core destroyed. Boss 1st attack. Boss 51% HP remained.
Rating: 10.9

17 Fury + 3 Synergy + 1 Shield
Night 10: 98 % remained
Night 11: Core destroyed. Boss 1st attack. Boss 59% HP remained.
Rating: 10.8

Boss Fight Test Conditions
21 full turrets equipped in the top, middle, bottom layers.
1 Guard troop
Night 11, Core HP 100 %, Boss 1st attack.
Boss is targeted (it's better than non targeting).
After the test, exit the game before Core destruction, and restart and load the game to go back to Night 11 for further test.

Boss Fight Test Summary by Rating
15 Fury + 3 Synergy + 3 Slowing Laser - Rating 20
16 Fury + 3 Synergy + 2 Slowing Laser - Rating 16.8
18 Fury + 3 Synergy + Last Bastion - Rating 15.4
17 Fury + 3 Synergy + 1 Shield - Rating 8.7
19 Fury + 2 Slowing Laser - Rating 8.7
21 Fury - Rating 8.6

Note
For boss fights, Fury, Synergy, Slowing Laser and Last Bastion seem to be very effective.

21 Fury
Night 11: Core destroyed. Boss HP 57 % remained.
Rating: 8.6

19 Fury + 2 Slowing Laser
First Test
Night 11: Core destroyed. Boss HP 54.5 % remained.
Rating: 9.1
Second Test
Night 11: Core destroyed. Boss HP 59.1 % remained.
Rating: 8.2
Average Rating: 8.7

17 Fury + 3 Synergy + 1 Shield
Night 11: Core destroyed. Boss 1st attack. Boss 56.4 % HP remained.
Rating: 8.7

16 Fury + 3 Synergy + 2 Slowing Laser
First Test
Night 11: Core HP 36 % remained. Boss 1st attack. Boss 50 % HP remained and fleed.
Rating: 15.6
Second Test
Night 11: Core HP 44 % remained. Boss 1st attack. Boss 50 % HP remained and fleed.
Rating: 17.9
Average Rating: 16.8

15 Fury + 3 Synergy + 3 Slowing Laser
First Test
Night 11: Core HP 36 % remained. Boss 1st attack. Boss 50 % HP remained and fleed.
Rating: 22.7
Second Test
Night 11: Core HP 36 % remained. Boss 1st attack. Boss 50 % HP remained and fleed.
Rating: 16.4
Average Rating: 20

18 Fury + 3 Synergy + Last Bastion
Night 11: Core HP 35 % remained. Boss 1st attack. Boss 50 % HP remained and fleed.
Rating: 15.4
Note: The Last Bastion turret absorbs 50% of Core damage and self-destructs in the morning. It costs 4 blue stones and 1 blue stone, if built in the lowest floor.

Based on the tests, the following configuration appears to be powerful, though I'm not sure if it's optimal.

Top layer:
Fury turrets + a Synergy turret

Middle layer:
Fury turrets + a Synergy turret

Bottom layer:
Fury turrets + a Synergy turret + a Shield turret
A Light Blade may be helpful.

Slowing Laser is very helpful for boss fight. To maximize thier effect, equip one of them in each layers. Slowing Laser's effectiveness on normal enemies should be tested further.

Laser turrets at the bottom layer would be powerful if you can decrease most of the enemies' HP below 50%. However they will not be effective against the first boss fight.

The Last Bastion turret, which absorbs 50% of Core damage and self-destructs in the morning, is very helpful in boss fights. It costs 4 blue stones and 1 blue stone, if built in the lowest floor.

Share your thoughts on the best turret combinations in the comments!

This defense game becomes significantly easier after defeating the boss, as the abundant resources allow for substantial defensive upgrades. My configuration focuses on maximizing the effectiveness of Fury and Teleport turrets:

Layer Configuration:
Top: 6 Fury Turrets + 1 Synergy Turret
Middle: 6 Fury Turrets + 1 Synergy Turret
Bottom: 6 Teleport Turrets + 1 Synergy Turret

Base facilities:
All of following facilities has x5 each:
Turret Beacon: +35% total attack range to all turrets.
Explosive Catalyst: +50% total attack rate to explosive turrets.
Energy Catalyst: +50% total attack rate to energy turrets.
Whirlwind Watch Tower: Pushes enemies back to the middle layer.
Turret Expander: (Night Skill) +175% total attack range to all turrets.
Nightbay: (Night Skill) Instantly charges night skills, once every 10 seconds.

The Nightbay towers keep the Turret Expander night skill almost permanently active. This allows the Teleport turrets on the bottom layer to continually push enemies back up to the top and middle layers.
The Fury turrets on these upper layers scorch the enemies with their high attack rate, extended range, and blazing area attacks, effectively covering both the top and middle areas.

Using this setup, I reached night 80 on difficulty 9 and could have easily continued much further.