1. SMG (small)
Uri, Dorsi, Taricus
1.1 As a pistol variant
Asea
2. Sub again (large)
UR,Asea
3. Rocket engine (medium)
Asea
3.1 Rocket Torpedo (medium)
Asea
3.2 Rocket Torpedo with solid fuel
3_1, UR
4. Monowing fighter plane (large)
Dorsi
5. Lighter, air-droppable torpedo (medium)
3_1, Uri, UR, Pat, Taricus.
6. Batteries (medium)
Asea, Uri, UR, Taricus.
7. Piranha midget submarine (large)
UR
8. Improve 15mm MG (small)
9. Design radio (small)
Asea
10. New aircraft engine (restart research, medium)
3_1, Uri, UR, Pat
11. Punisher torpedo boat (large)
UR
11.1 Without ram
3_1, Pat
12. Shark catamaran (large)
13. Armoured car (large)
Tar
14. Light tank (large)
Tar
A: 50 Ravens
A.1 Continually ravens
UR, 3_1, Asea, Uri, Dorsi
B. Shark Torpedo boats
C. Mass-produce warships
C.1 Expand Docks and produce sharks/protectors
UR, 3_1, Asea, Dorsi
D. Retool trucks to shark parts
UR, 3_1
E. Second raven factory
3_1, Pat, UR
Alpha: Procure combat-capable ships, Sell crow plans
UR
Beta: New wharf
Dorsi
Gamma: sell trucks
UR
Delta: Rocket propulsion works
Asea
Hotel: Train epsilon in aeroengineering and merge with delta.
Asea, Uri, 3_1, UR, Pat
Epsilon : Evacuate besieged islands through diplomacy.
Epsilon.1 : Same as above but includes open island if diplomacy fails.
Pat, 3_1.
Increased speed
Cheap
Easy to pilot
pat, Asea, Taricus
Easily maneuverable
dor, pat, 3_1, Asea, Uri, Taricus
Increased service ceiling
dor
Fuel efficient
UR, dor, pat
Aerodynamic
3_1, UR, Uri, Taricus
Silent
Enlarged ammunition drums
Resilient
UR, pat, 3_1, Asea, Uri
Variable speed
UR, 3_1, pat
Other detonator
Asea
Updated, your vote for Epsilon.1 was missing from the spoiler
.