Viewer

RoyaleViser shows a battle in a window: the arena, every unit, both hands and both elixir bars. It's the easiest way to see what your bot actually does. It runs as its own program, so it never slows training down, and when nobody is watching it costs almost nothing.

It comes with the install line and adds one command, royaleviser.

Watch Training Live

Turn on viser=True in the trainer:

learner = Learner(build_env, viser=True, save_dir="runs/my_bot")

Then, while it trains, open the viewer in a second terminal:

royaleviser

It finds the training run on its own and follows one of its battles as it happens. Close it and open it again whenever you like; training doesn't notice.

Watch a Saved Battle

play_battle plays one battle and saves it to a file the viewer can open:

from royalegym import make_env, play_battle

battle = play_battle(make_env(), blue="random", red="random", save_to="battle.msgpack")
print(battle.path)

battle.msgpack

royaleviser battle.msgpack

blue and red can each be "random", "noop", any opponent, or a bot you trained (Learner.load_policy("runs/my_bot")). To test your own bot on its own deck, pass your build_env() instead of make_env(). royaleviser battles/ opens the newest saved battle in a folder you saved battles to. Don't point it at your runs folder: training doesn't save battles, so it would open a training log.

Keys

Key	Does
Space	Play or pause.
Left / Right	Step one frame back or forward (with Shift: 20).
+ / -	Faster or slower.
f	Flip the board to the other side's view.
p	Show where each unit is walking.
t	Show what each unit is attacking.
g	Show the tile grid.
Click	Pin a unit to see everything about it, or jump along the timeline.
s	Save a picture.
h	List every key.
q	Quit.

Compare Two Battles

Give the viewer a second file and it draws that battle on top of the first, as see-through ghosts. Handy for seeing exactly where two versions of your bot made different choices:

royaleviser battle_a.msgpack --compare battle_b.msgpack

Watching Without the Trainer

Any environment can stream to the viewer. Hand it a ViserPublisher. Only do this in your own script that steps one environment, never in a build_env you train with Learner: the trainer builds many environments, and only one can stream at a time. With the trainer, use viser=True instead.

from royalegym import ClashParallelEnv, RustEngine
from royalegym.viser import ViserPublisher

env = ClashParallelEnv(RustEngine(), viser=ViserPublisher())

Then run royaleviser and step the environment as usual. Only one program at a time can stream, because the viewer listens on one fixed address.

The viewer's own guide, with every option, is in the RoyaleViser repository.