th07_multi_player

An experimental modification that lets two or three people play Touhou 7 ~ Perfect Cherry Blossom together. Built on the decompilation at some100/th07, with RUEEE/th06_multi_net as a reference for the multiplayer design.

The original game data (th07.dat and thbgm.dat) is not included. Supply it from your own legitimate copy of the game.

Current status

Three-player netplay has been confirmed working in testing.

This release also includes independent character/shot selection for all three players, shared-border handling, synchronized enemy drops, and predictive rollback across stage transitions.

v0.2.0

• Reworked the core multiplayer systems.
• Added multiplayer replay recording and playback.
• Added an optional lowlatency setting for input sampling and frame timing.
• Added F5/F6 controls to adjust input delay during rollback netplay.
• Delayed hit sounds until the hit is confirmed and suppressed duplicate sounds when rollback replays a frame.

v0.1.7

• Fixed the screen breaking up while paused.
• Window size and BGM can now be changed while waiting for a match to start.

v0.1.6

• Greatly reduced menu latency in multiplayer.
• Fixed sessions freezing after pausing.
• Failed rollback recovery now logs an error instead of freezing the game.

v0.1.5

• Added power transfer: overlap a partner and tap shot eight times to send them 20 power.

v0.1.4

• Added the Advanced settings section for optional bot, display, and diagnostic controls.
• Added Pin FPU control word for machines that may use different floating-point settings.

v0.1.3

• Fixed a rollback freeze caused by bomb-effect history overflow.
• Added optional netplay_trace.txt logging.
• Improved guest bot movement, item collection, boss positioning, and bomb usage.

v0.1.2

• Fixed a serious item-drop synchronization issue caused by item randomization.

This is still an experimental release, so other desyncs and bugs may remain.

Known issues

• A session can still desync. v0.1.2 fixed the known item-drop synchronization issue, but this does not guarantee that every possible cause has been found. If a session drifts apart, everyone should leave and rematch
• The title screen and the ending run very slowly in three player sessions. Both are outside the synchronized gameplay loop, and the extra peer makes them noticeably worse

What it does

• Two or three player netplay over UDP. The host is P1, the guests are P2 and P3; guest-to-guest input is relayed through the host
• The host must have the UDP port open/forwarded so guests can connect
• Local two player on one keyboard
• Each player picks their own character and shot type
• Lives, bombs and power are per player; cherry and score are shared
• Life transfer between players, and revival of a player who is out of lives
• Predictive rollback so movement is not held back by the round trip (selected by default; the host chooses the input delay)

Playing

1. Copy th07.dat and thbgm.dat next to th07_multi.exe
2. Everyone double-clicks th07_multi.exe, which opens the connection launcher
3. Choose Host or Guest under Connect as. Guests enter the host's IP address
4. Press the button below it (Start hosting or Connect to host)
5. When cur state lists the other players and Start Game lights up, the host presses it to start the game on every PC
6. In game, choose a character and shot for each player in turn

Start Game (local) in the same launcher starts a two player game on one PC.

Multiplayer replays are saved automatically as .mpr files in replay/. To watch one, choose Start Game (local) in the launcher, then select Replay from the game menu.

The host has to allow its UDP port through Windows Firewall. Playing over the internet also needs a port forward on the host's router.

Controls

In netplay each PC uses its own keyboard or pad with the original key layout, guests included.

Action	Key
Move	Arrow keys or numpad
Shot	Z
Bomb	X
Focus	Shift
Skip dialogue	Ctrl
Menu	Esc
Input delay during rollback netplay	F5 decreases by one frame; F6 increases by one frame

Pads use each PC's own th07.cfg, so configure them before matching. While the window is not focused the keyboard is ignored and only the pad is read.

Local two player shares one keyboard, so the second player uses a different set. The [KeyBind] section of mod_config.ini can change it.

Action	Key
Move	I / J / K / L
Shot	F
Bomb	G
Focus	D

There is no keyboard mapping for a third local player.

Launcher settings

The host chooses rollback and input delay; guests receive these session settings when they connect. Display and audio choices are local to each PC. The BOT checkbox in the launcher is intended for testing.

Advanced settings contains the optional lowlatency setting. It adjusts input sampling and frame timing to reduce latency. It is off by default and can be chosen separately on each PC.

What changes in multiplayer

• Boss health scales with the player count: 1x for one player, 0.75x for two, 2/3 for three
• Enemy drops produce one life or bomb item per active player, and anyone may collect any of them
• Power items are assigned to the players in rotation as they drop, and a drop becomes cherry only when the player it fell to is already at full power. A player who is not at full power keeps receiving power
• Point item extends are granted to everyone when the threshold is reached
• Life transfer: overlap two ships within 20 pixels, then release shot and hold focus for 90 frames. A life item homes to the other player; a player who is out of lives is revived directly
• Power transfer: overlap two ships within 20 pixels and tap shot eight times. Twenty power crosses as power items that home to the other player. A counter appears over the ship from the fourth tap. It only offers itself when the giver has twenty to spare and the partner is short of full power
• Unlocks for Extra, Phantasm, every character and every practice stage are forced in memory so that differing score.dat progress cannot change the synchronized menu structure. Nothing is written back to the save
• The difficulty cursor always starts at Normal
• Rank loses less to a death or a bomb than in single player, divided by the player count, so that three ships losing lives do not flatten the difficulty curve three times as fast

Predictive rollback

Predictive rollback continues using recent remote input until the actual input arrives. If the prediction differs, the game rewinds to the affected frame and replays the simulation. If an input remains missing beyond the prediction window, play waits for it.

Building

A 32-bit Windows build using MSVC 19.10 (Visual Studio 2017), the Windows 10 SDK, and the DirectX 8 SDK. Put the compiler under prefix/msvc1410, or set TH07_PREFIX to a checkout containing that prefix.

python scripts/build.py

The result is build/th07_multi.exe. The build script fetches the DirectX 8 SDK files if they are missing.

Limitations

• Experimental. There is no NAT traversal and no encryption
• A NAT rebind after matching cannot be recovered from
• Intended for playing with people you trust, not for a public server
• Everyone must run the same th07_multi.exe and the same game data
• Latency or packet loss beyond the prediction window stalls the game while it waits for the missing input

Data and rights

Do not redistribute th07.dat or thbgm.dat. They are required to run, but each player supplies them from their own copy of the game.

Rights over the decompiled portion follow some100/th07.

Credits

• some100/th07 for the decompilation this is built on
• RUEEE/th06_multi_net for the multiplayer design it follows