Propa.

Propa. is a strategy game in which you command a virus, invade host cells and fight the immune system. You use the cells’ replication mechanisms to multiply and spread, adapting your virus as the immune response changes.

Battles inside cells

Cells are the main battlegrounds. You direct viral units into host cells, where they use replication mechanisms in the cell nucleus to reproduce. As the virus multiplies, it gradually activates the host cell’s apoptosis signaling pathway, leading to programmed cell death. Some victories require destroying every cell; in others, you need to leave some alive so they can continue supplying resources for viral replication.

As your virus units grow in number, the immune system produces signaling molecules to hinder their spread:

• Apoptosis inducers: activate host-cell apoptotic pathways, quickly eliminating viral units that cannot escape in time.
• Target host cell receptors: bind to receptors for spike proteins on host-cell surfaces, competing with viruses and blocking their entry.
• Nucleoside analogues: interfere with replication in the host-cell nucleus, causing errors in the viral genome and the loss of critical genetic fragments.
• Budding inhibitors: prevent replicated viruses from leaving host cells by budding, limiting their spread.

Surface antigens

Each viral unit carries a unique set of four surface antigens, molecular structures made up of randomly combined colors and shapes. White blood cells recognize these antigens and engulf the viruses. You can generate new antigens through mutation to evade recognition, but when viruses sharing a particular set of antigens become numerous, the immune system gradually learns to recognize them and strengthens its response. Managing the types and quantities of antigens can therefore be crucial.

Genetic fragments

Each virus can carry up to four genetic fragments. The game includes fragments with different functions:

• Spike Protein Fragment: the most common type; unlocks the host-cell membrane so the virus can enter and replicate.
• Budding Protein Fragment: lets the virus leave the host cell after replication.
• Acceleration Fragment: speeds up viral replication inside the host cell.
• Blocker Fragment: reduces the ability of host white blood cells to engulf viruses.
• Mutation Fragment: lets the virus change into other genetic fragments with special abilities during replication, increasing its diversity and adaptability.
• Hemorrhagic Fever Fragment: directly damages host endothelial cells, harming blood vessel walls and causing persistent bleeding.
• Signal Suppression Fragment: suppresses immune signaling molecules within a certain range, preventing host cells from undergoing apoptosis or functional changes.
• Antigen Conversion Fragment: erases the surface antigens of viruses within a certain range, so white blood cells cannot recognize or engulf them.
• Regulation Fragment: repairs host-cell surface structures exploited by the virus, delaying premature cell lysis and apoptosis to maintain an environment for viral replication.

You monitor environmental changes and adjust your strategy, combining genetic fragments and surface antigens to counter the immune system. By optimizing the virus’s functions, you pursue its spread and evolution across the world.