help: Add 'Why did I lose?' help topic (#4217)

* Draft 'Why did I lose?' help topic

* fixup! Draft 'Why did I lose?' help topic

Implement @beetlenaut's suggestions

* help: Change to title case for consistency with the rest of the section

* help: Explain the term 'foreknowledge'

data/core/help.cfg

@@ -25,7 +25,7 @@
     [section]
         id=gameplay
         title= _ "Gameplay"
-        topics=..gameplay,victory_and_defeat,recruit_and_recall,income_and_upkeep,hitpoints,advancement,movement,shroud_and_fog,combat,damage_types_and_resistance,orbs,time_of_day,healing,saveload,wrap_up
+        topics=..gameplay,victory_and_defeat,recruit_and_recall,income_and_upkeep,hitpoints,advancement,movement,shroud_and_fog,combat,damage_types_and_resistance,orbs,time_of_day,healing,saveload,whylost,wrap_up
     [/section]
 
     [section]
@@ -175,7 +175,7 @@ The interactive <bold>text='Tutorial'</bold> introduces the basics of Wesnoth ga
 
 After you master the basics, try out a beginner campaign, such as <italic>text='Heir to the Throne'</italic> or <italic>text='The South Guard'</italic>. A full list of installed campaigns can be found via the <bold>text='Campaign'</bold> option on the main menu. As Wesnoth can be quite challenging, you may wish to start on easy before progressing to higher difficulties.
 
-Campaigns are grouped by <italic>text='level'</italic> and <italic>text='difficulty'</italic>. For example, <italic>text='Heir to the Throne'</italic> is ‘Novice’ level, and is playable at three difficulties: ‘Beginner’, ‘Normal’, and ‘Challenging’. The level of a campaign indicates what degree of proficiency in the game mechanics (such as <ref>dst='movement' text='zones of control'</ref> and <ref>dst='time_of_day' text='time of day'</ref>) is assumed. The difficulty indicates how challenging the scenarios will be to a veteran player: at higher difficulties, the obstacles to victory will be higher and overcoming them will require more skillful play." + "
+Campaigns are grouped by <italic>text='level'</italic> and <italic>text='difficulty'</italic>. For example, <italic>text='Heir to the Throne'</italic> is ‘Novice’ level, and is playable at three difficulties: ‘Beginner’, ‘Normal’, and ‘Challenging’. The level of a campaign indicates what degree of proficiency in the game mechanics (such as <ref>dst='movement' text='zones of control'</ref> and <ref>dst='time_of_day' text='time of day'</ref>) is assumed. The difficulty indicates how challenging the scenarios will be to a veteran player: at higher difficulties, the obstacles to victory will be higher and overcoming them will require more skillful play. For example, at higher difficulties the enemy may have higher incomes, higher-level units, more castle hexes, and so on." + "
 
 <img>src=help/tooltip.png align=right float=yes</img>" +
             _ "While playing, keep in mind that you can mouse-over many items in the game, such as the information displayed in the status pane, to see a brief description explaining each item. This is especially useful when you encounter new elements, such as <ref>dst='..abilities_section' text='abilities'</ref>, for the first time." + _ "
@@ -296,6 +296,45 @@ In the mainline campaigns, on hard:
 That said, it’s a game; the best way to play it is whichever way gives you the most enjoyment."
     [/topic]
 
+    [topic]
+        id=whylost
+        title= _ "Learning from Losses"
+        text= _ "<italic>text='Why did I lose that scenario?'</italic>
+
+One of the most difficult parts of Wesnoth is understanding why a scenario was lost.
+
+When you first start playing, you will probably lose some scenarios. That is normal, and is part of learning the game. When that happens, try to learn from your mistakes: watch the replay, try to understand what you did wrong, then <ref>dst='saveload' text='restart the scenario'</ref> and try again.
+
+Some common reasons for losing a scenario are:
+
+• Playing a campaign at too high a <ref>dst='..gameplay' text='difficulty level'</ref>. Try restarting the scenario at an easier difficulty.
+
+• Playing a poor strategy: for example, recruiting the wrong types of units, fighting at the wrong <ref>dst='time_of_day' text='time of day'</ref>, not taking advantage of terrain features or units’ special abilities, and so on.
+
+• Missing clues. Often there will be hints in the campaign’s story and dialog about what to expect from a difficult scenario and how to prepare for it. If you have a loyal mage on your side, take the time to listen to its advice; it may save your life.
+
+• Barely scraping a victory in a previous scenario. At all difficulties except “Beginner” (TODO: and “Easy”?), campaigns assume that you will have some <italic>text='carryover gold'</italic> and some advanced units on your <italic>text='recall list.'</italic> (These concepts are explained in the tutorial.) If you win a scenario but lose most of your advanced units and much of your gold, the following scenario may be very difficult to beat, even for a more experienced player. If you find yourself in this situation, you may try to go back a scenario or two and win them more convincingly, or change to an easier difficulty. (However, remember that <italic>text='some'</italic> losses are expected, particularly at higher difficulties.)
+
+• Poor gold management. At higher difficulties, managing gold — capturing villages to increase the income, and using low-level units and fresh recruits to reduce the spending — becomes important. If you use many high-level units, you might win a scenario easily but have not enough gold carryover for the next scenario. (This would be an example of “barely scraping a victory”.)
+
+<header>text='Unlikely reasons'</header>
+
+In addition to the common reasons, listed above, there are a few other reasons which are unlikely, though not impossible. They are:
+
+• You may have played a strategy that the campaign developer did not anticipate, and ended up with a set of high-level units not suitable for the next scenario.
+
+• You may have found a scenario that can only be won on the second or third time through, whether by requiring above-average luck or by expecting the players to have foreknowledge — to know what surprises are coming up before they happen. (It is under discussion whether foreknowledge is expected at the highest difficulties. Requiring above-average luck, however, would qualify as a bug.)
+
+• Unusually-bad luck. Whether an attack hits or misses is random, so it could happen that the enemy was very lucky and had many hits, while you were very unlucky and had many misses. However, this is a very rare occurrence, virtually unheard of in all but the shortest, smallest scenarios. In fact, losses are more commonly caused by playing a <italic>text='bad'</italic> strategy despite having <italic>text='above-average'</italic> luck, than by playing a <italic>text='good'</italic> strategy but having <italic>text='below-average'</italic> luck. Moreover, merely having “below-average” luck does not excuse a loss; having below-average luck is perfectly normal, and scenarios are designed to be winnable even with below-average luck. It is only exceedingly bad luck, over multiple turns, that we mean here.
+
+Be wary of attributing a loss to any of these reasons. If you are not a veteran player, it is far more likely that your loss was caused by one of the <italic>text='common'</italic> errors, listed above, and is not indicative of a bug in the campaign. However, if you still think you found a bug, then by all means, report it!
+
+The “Damage Calculations” dialog shows some statistics that can help determine whether a match was very lucky or very unlucky. However, reading the statistics is no substitute to watching the replay and looking for strategic mistakes, or small bits of luck at critical points in the engagement.
+
+TODO: link to a forum thread where new players can post their replays and get review/corrections (like https://forums.wesnoth.org/viewtopic.php?f=3&t=39944 but specifically for new players)?
+"
+    [/topic]
+
     # wmllint: markcheck off
     [topic]
         id=combat