The Goal

Don't get destroyed by the troll.

Rules

If you have stones, shoot 1 or more of them.
If you don't have stones, shoot 0 exactly.

Rule Evolution

The following ideas are still in flux, waiting for some opinions. Please drop a word on the contribution's page or on the forum

Is it even worth publishing? can the problem be totally solved?
More maps? (a map is a {road length} × {initial stone count} pair)
Leagues? I could conceive the referee being permissive (allow 0 stones thrown) in the first one, and then strict.
Fog of war? (see only troll position, not enemy throw/stones left)
variable for of war? (seeing enemy stones is a boolean decided randomly as part of the map?
alternative fog of war? (seeing enemy stones only when troll is close to us?)
Praise for my artistic skillz
Other remarks?

Victory Condition

Your opponent loses.

Defeat Condition

The troll reaches your castle.
When no player has stones left, the troll is closer to your castle.

I/O Protocol

Just read the sample code. You can figure this out.
You're currently allowed the default SDK timings. I think it's one second for the first turn and 50 ms then, but don't quote me on this.

Maps

The following maps are currently available and randomly yet extremely fairly (you wouldn't believe the effort that went into this) chosen uniformly at random among the following:

Road length	Stones
6	15
6	30
14	30
14	50

As with anything in this draft statement, this is subject to change without notice. Why do you think they're provided in the game input?

Change Log

This is computer science. Trees are non-negociable. (asset contributed by Alshock )
Don't destroy the castle if the troll doesn't reach it.
Ensure proper troll movement direction in all cases of cheating.
Fixed the road length fencepost non-issue.
Of course that game needed MSG functionality!
Enforce the one-stone rule. (that also fixed the legacy buh—sorry people! I put an easter egg in exchange)
Cutesy defeat animations.
Distinct castle sprites!
Terminate game when there are no more stones in sight.
More pretty. (SRLSLY)
No more void maps. (root cause: Java % on a negative seed)

“Trolls simply detest the very sight of dwarves (uncooked).”

— J.R.R. Tolkien, The Hobbit

Based on an involuntary suggestion by Zaap38 on the #Fr channel. The original appears to be by Romain André-Lovichi .

The source code for this game is available.