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		<updated>2026-04-15T14:35:38Z</updated>
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	<entry>
		<id>https://www.explainxkcd.com/wiki/index.php?title=1403:_Thesis_Defense&amp;diff=223597</id>
		<title>1403: Thesis Defense</title>
		<link rel="alternate" type="text/html" href="https://www.explainxkcd.com/wiki/index.php?title=1403:_Thesis_Defense&amp;diff=223597"/>
				<updated>2022-01-04T20:29:52Z</updated>
		
		<summary type="html">&lt;p&gt;Abigblueworld (real): &lt;/p&gt;
&lt;hr /&gt;
&lt;div&gt;“What?” Also, Say you and no one else!&lt;br /&gt;
&lt;br /&gt;
==Explanation==&lt;br /&gt;
In the comic, [[Megan]] is presenting evidence on her {{w|thesis}}, a theory on the evolution of threat displays in mammals, in front of a panel of some people. To conclude her exposition she charges at the audience, shouting a {{w|battle cry}}, and brandishing a sword. The audience flinches. As the audience is composed of mammals and is responding to a displayed threat, we should assume that this response provides some key evidence about the threat displays in mammals.&lt;br /&gt;
&lt;br /&gt;
This comic is a play on a thesis defense and the {{w|adage}} &amp;quot;{{w|The best defense is a good offense}}&amp;quot;. The adage means that a strong offensive action will preoccupy the opposition and ultimately hinder its ability to mount an opposing counterattack, leading to a strategic advantage. A thesis defense generally involves an oral exam on the topic the candidate has chosen, and should involve no physical violence.&lt;br /&gt;
&lt;br /&gt;
For added humorous effect, in the title text Megan extrapolates how she improved the state of the art, i.e. what she has added to her field of study, while screaming the word art.&lt;br /&gt;
&lt;br /&gt;
==Transcript==&lt;br /&gt;
:[Megan runs towards a desk with two microphones on it, waving a broadsword high in the air. Cueball and one other sitting behind the desk are taken aback, while Ponytail standing off to the side holds an arm in front of her face protectively. A slide is projected on a screen behind Megan, reading &amp;quot;The evolution of threat displays in mammals&amp;quot;.]&lt;br /&gt;
:Megan: In conclusion, AAAAAAAAAAAAA!!!&lt;br /&gt;
:[Caption below the panel:]&lt;br /&gt;
:The best thesis defense is a good thesis offense.&lt;br /&gt;
&lt;br /&gt;
{{comic discussion}}&lt;br /&gt;
[[Category:Comics featuring Cueball]]&lt;br /&gt;
[[Category:Comics featuring Megan]]&lt;br /&gt;
[[Category:Comics featuring Ponytail]]&lt;br /&gt;
[[Category:Multiple Cueballs]]&lt;/div&gt;</summary>
		<author><name>Abigblueworld (real)</name></author>	</entry>

	<entry>
		<id>https://www.explainxkcd.com/wiki/index.php?title=372:_To_Be_Wanted&amp;diff=223596</id>
		<title>372: To Be Wanted</title>
		<link rel="alternate" type="text/html" href="https://www.explainxkcd.com/wiki/index.php?title=372:_To_Be_Wanted&amp;diff=223596"/>
				<updated>2022-01-04T20:29:22Z</updated>
		
		<summary type="html">&lt;p&gt;Abigblueworld (real): &lt;/p&gt;
&lt;hr /&gt;
&lt;div&gt;“What?” Also, Say you and no one else!&lt;br /&gt;
&lt;br /&gt;
==Explanation==&lt;br /&gt;
The comic begins with a grainy pencil-drawing of [[Megan]] on a ship. This is a clue that things are not as they appear.&lt;br /&gt;
&lt;br /&gt;
As the point-of-view pulls back in each successive frame, we see that &amp;quot;Megan on a ship&amp;quot; is really a {{w|Thought bubble#Thought bubbles|thought-bubble}} belonging to [[Cueball]], who is sitting at his desk. He apparently is day-dreaming instead of working. This is presented in the standard, crisp format, as if drawn on a computer. This suggests it shows us our &amp;quot;normal&amp;quot; view.&lt;br /&gt;
&lt;br /&gt;
However, as the perspective continues to pull back, we see that &amp;quot;Cueball thinking of Megan&amp;quot; is actually a thought-bubble belonging to Megan. In the final frames, the ship sails out of frame. However, since the final frames are in the same grainy pencil-drawing format, it suggests that this is still Cueball's thoughts, rather than an actual image of Megan.&lt;br /&gt;
&lt;br /&gt;
The title text, &amp;quot;Or so I hope,&amp;quot; shows us what this {{w|recursion}} really means: Cueball hopes that Megan realizes that he misses her, but suggests he's not entirely certain she does.&lt;br /&gt;
&lt;br /&gt;
But, the comic can be interpreted in a different manner. &lt;br /&gt;
&lt;br /&gt;
;Alternative explanation&lt;br /&gt;
The comic starts with Megan on the bow of a ship, but in following panels, it turns out that Cueball (presumably in a relationship with Megan) is thinking about about her, sitting afar from her. As we move forward (or downwards) in the comic, it turns out indeed that Megan is thinking that her partner Cueball might be missing her and thinking about her while she is on a voyage, or at least she hopes it to be that way, as the title text suggests. This also explains the title of the comic &amp;quot;To Be Wanted,&amp;quot; which Megan expects from Cueball.&lt;br /&gt;
&lt;br /&gt;
Both of the above explanations could be true without conflict. But as the title text is most often assigned to [[Randall]] himself or to a Cueball character, the &amp;quot;Or so I hope?&amp;quot; is most likely written by the guy who drew the comic. This would then indicate that it is Cueball/Randall who wishes to be wanted by Megan - but he also hopes that Megan knows/hopes that he wants her.&lt;br /&gt;
&lt;br /&gt;
==Transcript==&lt;br /&gt;
:[Megan stands looking out on the bow of a ship.]&lt;br /&gt;
:[Scene backs up. More of the boat is shown.]&lt;br /&gt;
:[Scene backs up. The boat with Megan is within a thought bubble.]&lt;br /&gt;
:[Scene backs up. The thought bubble comes from Cueball sitting at a computer in an office.]&lt;br /&gt;
:[Scene repeated for the next frame.]&lt;br /&gt;
:[Scene backs up. Cueball is within yet another thought bubble.]&lt;br /&gt;
:[Scene backs up. The thought bubble with Cueball in it belongs to Megan at the bow of the ship.]&lt;br /&gt;
:[The thought bubble disappears, showing only Megan in the boat.]&lt;br /&gt;
:[The boat sails out of view.]&lt;br /&gt;
&lt;br /&gt;
{{comic discussion}}&lt;br /&gt;
[[Category:Comics featuring Megan]]&lt;br /&gt;
[[Category:Comics featuring Cueball]]&lt;/div&gt;</summary>
		<author><name>Abigblueworld (real)</name></author>	</entry>

	<entry>
		<id>https://www.explainxkcd.com/wiki/index.php?title=399:_Travelling_Salesman_Problem&amp;diff=223595</id>
		<title>399: Travelling Salesman Problem</title>
		<link rel="alternate" type="text/html" href="https://www.explainxkcd.com/wiki/index.php?title=399:_Travelling_Salesman_Problem&amp;diff=223595"/>
				<updated>2022-01-04T20:29:07Z</updated>
		
		<summary type="html">&lt;p&gt;Abigblueworld (real): &lt;/p&gt;
&lt;hr /&gt;
&lt;div&gt;“What?” Also, Say you and no one else!&lt;br /&gt;
&lt;br /&gt;
==Explanation==&lt;br /&gt;
The {{w|Travelling salesman problem|travelling salesman problem}} is a classic problem in computer science. An intuitive way of stating this problem is that given a list of cities and the distances between pairs of them, the task is to find the shortest possible route that visits each city exactly once and then returns to the origin city. A naïve solution solves the problem in {{w|Factorial|O(n!) time}} (where n is the size of the list), simply by checking all possible routes, and selecting the shortest one. However, this approach will take a long time as the number of possible routes increases exponentially as more nodes are included.&lt;br /&gt;
&lt;br /&gt;
A more efficient {{w|Dynamic programming|dynamic programming}} approach yields a solution in O(n&amp;lt;sup&amp;gt;2&amp;lt;/sup&amp;gt;2&amp;lt;sup&amp;gt;n&amp;lt;/sup&amp;gt;) time. These times are given using {{w|Big O notation}}, which is commonly used in computer science to show the efficiency or complexity of a solution or algorithm.&lt;br /&gt;
&lt;br /&gt;
The joke is that the salesman selling online (say on {{w|eBay}}, {{w|Amazon Marketplace}}, or other virtual marketplace) does not have to worry about this problem, since he does not need to travel (which makes the time to find the best solution O(1)), to which the travelling salesman angrily responds, &amp;quot;Shut the hell up.&amp;quot;&lt;br /&gt;
&lt;br /&gt;
The title text wonders about the time complexity of the {{w|Cutting-plane method|cutting-plane method}}, which is sometimes used to solve optimization problems.&lt;br /&gt;
&lt;br /&gt;
The last sentence suggests the downside for Randall of drawing comics about computer science; he sometimes encounters problems to which he cannot find the answer, whereas authors of simpler comics such as {{w|Garfield}} do not have this problem. This is also likely a reference to [[78: Garfield]], which parodies Garfield's simplicity.&lt;br /&gt;
&lt;br /&gt;
The map almost certainly depicts the United States, with the locations highlighted suspected to be (from left to right): Seattle, San Francisco, Los Angeles, Phoenix, Denver, Minneapolis, Dallas, San Antonio, Houston, Chicago (cut off), Detroit, Atlanta, Miami, Washington D.C., Philadelphia, New York, and Boston.&lt;br /&gt;
&lt;br /&gt;
This is so far the only comic featuring the Brown Hat character.&lt;br /&gt;
&lt;br /&gt;
Also see earlier strip [[287: NP-Complete]].&lt;br /&gt;
&lt;br /&gt;
==Transcript==&lt;br /&gt;
:[There is a linked black web, with a path in red; it appears to be a map of the United States.]&lt;br /&gt;
:Brute-force solution:O(n!)&lt;br /&gt;
:[The web continues in this one. A man with a brown hat and a case is drawing it.]&lt;br /&gt;
:Dynamic programming algorithms: O(n&amp;lt;sup&amp;gt;2&amp;lt;/sup&amp;gt;2&amp;lt;sup&amp;gt;n&amp;lt;/sup&amp;gt;)&lt;br /&gt;
:[Another man, with a brown hat too, is at a computer, looking back over the chair.]&lt;br /&gt;
:Selling on eBay: O(1)&lt;br /&gt;
:eBay salesman: Still working on your route?&lt;br /&gt;
:Drawing salesman: Shut the hell up.&lt;br /&gt;
&lt;br /&gt;
{{comic discussion}}&lt;br /&gt;
[[Category:Comics with color]]&lt;br /&gt;
[[Category:Math]]&lt;br /&gt;
[[Category:Programming]]&lt;/div&gt;</summary>
		<author><name>Abigblueworld (real)</name></author>	</entry>

	<entry>
		<id>https://www.explainxkcd.com/wiki/index.php?title=2246:_Christmas_Presents&amp;diff=223594</id>
		<title>2246: Christmas Presents</title>
		<link rel="alternate" type="text/html" href="https://www.explainxkcd.com/wiki/index.php?title=2246:_Christmas_Presents&amp;diff=223594"/>
				<updated>2022-01-04T20:28:48Z</updated>
		
		<summary type="html">&lt;p&gt;Abigblueworld (real): &lt;/p&gt;
&lt;hr /&gt;
&lt;div&gt;“What?” Also, Say you and no one else!&lt;br /&gt;
&lt;br /&gt;
==Explanation==&lt;br /&gt;
This is the second comic in a row about presents, this one in particular calls them {{w|Christmas gift|Christmas presents}}, and it was also released on {{w|Christmas}} Day. This is the second [[:Category:Christmas|Christmas comic]] in a row after [[2245: Edible Arrangements]].&lt;br /&gt;
&lt;br /&gt;
A {{w|Christmas tree}} cut down from the woods will typically be placed in a living-room soon after being cut down, and left standing there through the holiday season. On {{w|Christmas Eve}} or {{w|Christmas Day}}, or even earlier, presents are typically put beneath the tree under the lower branches. Once the tree is cut down, it will eventually start turning brown and/or losing its needles as it no longer receives any nutrients from its roots.{{Citation needed}}&lt;br /&gt;
&lt;br /&gt;
Based on this observation (on Christmas Day) some biologist (or [[Randall]]) concludes that the presents are a type of {{w|parasitic plant}}—that is, a plant that derives some or all of its nutritional requirement from another living plant. Since such a plant can use the sugars produced by the parasitised tree it does not necessarily have to perform photosynthesis by itself (although some parasitic plants such as mistletoe are photosynthetically active). If the parasitic plant is not doing photosynthesis it can live in the shade beneath a tree that it parasitizes as it has no need for light, and since it does not need chlorophyll either, it may not be green (e.g. {{w|Orobanche}}).&lt;br /&gt;
&lt;br /&gt;
With  presents often being wrapped in bright white and red colored paper, Randall concludes that this indicates a lack of chlorophyll, thus fitting with the idea of a parasitic plant. With the presents being in the shade of the tree and the tree's health suffering, the evidence can only lead to the conclusion that Christmas presents are parasitic plants.&lt;br /&gt;
&lt;br /&gt;
In the title text a biologist says that &amp;quot;The parasitism might be mediated by a fungus!&amp;quot;  While many parasitic plants attach themselves directly to the plant they are parasitising (e.g. {{w|mistletoe}}, a parasitic plant which is often used to symbolize romance at Christmas) this is obviously not the case with the Christmas presents which are not growing out of the Christmas tree - which appears to rule out a parasitic relationship. However, the biologist has an answer for that: Some parasitic plants (such as {{w|sarcodes|snow flowers}}) do not attack the tree directly but instead form a connection to mycorhizal {{w|Fungus|fungi}}. These fungi are receiving sugars from the trees and in turn provide it with mineral nutrients. By parasitising these fungi the snow flower can steal the sugars of the tree indirectly, one says that the fungi is mediating the parasitism.&lt;br /&gt;
&lt;br /&gt;
Randall dismisses these words as coming from a biologist who is &amp;quot;trying to ruin Christmas again&amp;quot;, which could have several meanings.  It could be that the biologist really is just trying to ruin Christmas, and is trying to be more successful than in previous years by tying Christmas presents to fungus in people's minds.  One might say that the biologist is not a &amp;quot;fun guy&amp;quot; for doing this. {{Citation needed}}&lt;br /&gt;
&lt;br /&gt;
It could instead be the case that the biologist is quite earnest in his belief that Christmas presents are harmful plant parasites and is attempting to spray the presents with a {{w|fungicide}}, which would probably be toxic and potentially contaminate not only the wrapping paper but also the presents inside their boxes. &lt;br /&gt;
&lt;br /&gt;
Finally, it could be that the biologist is right, and Christmas presents are hosts to or otherwise associated with a parasitic fungus (and Randall's dismissal is a sign of his infection).  There are some parasitic fungi that hijack the brains of host animals and alter their behavior.  The most famous of these is probably ''{{w|Ophiocordyceps unilateralis}}'', the so-called &amp;quot;zombie ant fungus&amp;quot;, which causes its hosts to perch on a high plant to maximize the distance traveled by the fungus's spores.  Ants have in turn developed strategies for detecting and removing infected members from the colony's territory.  None of these fungi are known to infect humans, but they did inspire the zombie fungus in ''{{w|The Last of Us}}''.&lt;br /&gt;
&lt;br /&gt;
==Transcript==&lt;br /&gt;
:[A Christmas tree decorated with 16 balls and a star at the top with a high trunk with space for several presents beneath. About 13 presents with different patterns of paper and some with strings around. Three arrows with text at the blunt end points towards different areas. To the left one points to a present, beneath this one points to the area beneath the tree (the bottom of one present) and  to the right one points to the tree.]&lt;br /&gt;
:Bright white and red colors indicate a lack of Chlorophyll&lt;br /&gt;
:Flourishing in the shade&lt;br /&gt;
:Tree health suffering&lt;br /&gt;
&lt;br /&gt;
:[Caption beneath the panel:]&lt;br /&gt;
:The evidence is clear: Christmas presents are parasitic plants.&lt;br /&gt;
&lt;br /&gt;
{{comic discussion}}&lt;br /&gt;
&lt;br /&gt;
&amp;lt;!-- Include any categories below this line. --&amp;gt;&lt;br /&gt;
&lt;br /&gt;
[[Category:Christmas]]&lt;br /&gt;
[[Category:Biology]]&lt;/div&gt;</summary>
		<author><name>Abigblueworld (real)</name></author>	</entry>

	<entry>
		<id>https://www.explainxkcd.com/wiki/index.php?title=618:_Asteroid&amp;diff=223593</id>
		<title>618: Asteroid</title>
		<link rel="alternate" type="text/html" href="https://www.explainxkcd.com/wiki/index.php?title=618:_Asteroid&amp;diff=223593"/>
				<updated>2022-01-04T20:28:32Z</updated>
		
		<summary type="html">&lt;p&gt;Abigblueworld (real): &lt;/p&gt;
&lt;hr /&gt;
&lt;div&gt;“What?” Also, Say you and no one else!&lt;br /&gt;
&lt;br /&gt;
==Explanation==&lt;br /&gt;
The comic begins with [[Blondie]] as a [[:Category:News anchor|news anchor]] reporting that an asteroid is headed for Earth.&lt;br /&gt;
&lt;br /&gt;
The end of the world has been envisioned in many ways. One of the most common is with a really big rock hitting Earth. This has been depicted in movies several times, most famously, and released in the same year, are {{w|Armageddon (1998 film)|Armageddon}} and {{w|Deep Impact (film)|Deep Impact}}, but also {{w|The Day the Sky Exploded}} and many more. These  lists of films {{w|Asteroid (film)|with asteroids}} and {{w|Meteor (film)|meteors}} show how popular this theme is. &lt;br /&gt;
&lt;br /&gt;
There is an [http://impact.ese.ic.ac.uk/ImpactEffects online calculator] for asteroid impacts, but don't worry, as any rock that does hit Earth [http://blog.seattlepi.com/thebigblog/2010/11/04/calculator-shows-effects-of-asteroid-collision-with-earth isn't likely] to kill [http://www.sott.net/article/124099-Catastrophe-Calculator-Estimate-Asteroid-Impact-Effects-Online everyone]. And, as seen in the [[what if?]] ''{{what if|20|Diamond}}'', speed counts too.&lt;br /&gt;
&lt;br /&gt;
The joke here, though, is that, after sending up a robot to blow the asteroid to smithereens, said rock is actually the home of {{w|the Little Prince}} from the famous tale by Antoine de Saint-Exupéry. To save our world, we must destroy his. And probably the prince along with it. If the only way to save our species is by killing off another species, is the act still ethical? In none of the world-destroying asteroid stories were said rocks actually home to intelligent life. Or any life, for that matter. A second joke that can be seen is that in said movies the &amp;quot;heroic&amp;quot; mission always involves humans in some way imperiling themselves to save humanity, rather than, say, staying safely at home and using a robotic rover to do all the dangerous stuff. &lt;br /&gt;
&lt;br /&gt;
The title text is a reference to the 1998 asteroid movie {{w|Deep Impact (film)|Deep Impact}}. &amp;quot;Crossover&amp;quot; is a term used to refer to a technique of taking two independent (and usually already existing) stories and creating a scene or short story in which characters from both worlds collide and interact with each other. Or, in other words, characters from one story &amp;quot;crossover&amp;quot; into the second. Fanfic is short for {{w|Fan Fiction}}, e.g. a fictional story written by someone who loves a particular story/series/idea so much they wanted to write their own tale about it (or one who hated said story so much they felt compelled to fix it). It suggests that most people were unwilling to read a story about people nuking miniature kingdoms to save civilization. A tough entertainment call any day.&lt;br /&gt;
&lt;br /&gt;
The Little Prince was referenced already back in [[2: Petit Trees (sketch)]] and later again in [[1350: Lorenz]] at [http://imgs.xkcd.com/comics/a1-2014/VgSdMz8OAHQ8w5Ee432f5Q.png the end] of the space trip branch.&lt;br /&gt;
&lt;br /&gt;
==Transcript==&lt;br /&gt;
:[Blondie as a news anchor is standing in front of a screen pointing to a diagram of an asteroid's trajectory path with Earth in the path. There is a caption below the screen:]&lt;br /&gt;
:Blondie: Astronomers have confirmed that the asteroid is headed for Earth.&lt;br /&gt;
:Caption: Breaking news&lt;br /&gt;
&lt;br /&gt;
:[In a frame-less panel Blondie narrates above a picture of a rocket with fire out the end of its two lifter rockets on either side of the central main part of the rocket. It flies up and right. In an inset picture to the right and below the rocket there is an image of a rover with text on it. The rower has two legs and a drill below it, and an antenna above the main body of the rower.]&lt;br /&gt;
:Blondie (narrating): NASA has launched a heroic mission to land a rover on the asteroid, drill into it, and destroy it with nuclear bombs.&lt;br /&gt;
:Rover: NASA&lt;br /&gt;
&lt;br /&gt;
:[Ponytail is sitting in an office chair at the control panel of a large unit using it. Cueball stands in front of it looking away from her to the right. Both are wearing headsets with microphones. A voice speaks to them from off-panel right.]&lt;br /&gt;
:Ponytail: The robot has landed successfully and planted the nukes! We're saved!&lt;br /&gt;
:Cueball: Hooray!&lt;br /&gt;
:Voice (off-panel): We're heroes!&lt;br /&gt;
&lt;br /&gt;
:[The Little Prince is standing on his small asteroid next to his rose and a very small volcano. He is looking at the NASA rover which is partly outside the panel to the right and up. Two legs and the drill can be seen as well as part of the antenna and the part of the body with the text. The rover has drilled into the asteroid. There is a digital countdown emanating from the rover above the Prince.]&lt;br /&gt;
:0:05...&lt;br /&gt;
:0:04...&lt;br /&gt;
:0:03...&lt;br /&gt;
:Rover: NASA&lt;br /&gt;
&lt;br /&gt;
{{comic discussion}}&lt;br /&gt;
&lt;br /&gt;
[[Category:Comics featuring Blondie]] &lt;br /&gt;
[[Category:Comics featuring Cueball]]&lt;br /&gt;
[[Category:Comics featuring Ponytail]]&lt;br /&gt;
[[Category:News anchor]]&lt;br /&gt;
[[Category:Fiction]]&lt;br /&gt;
[[Category:Space probes]]&lt;br /&gt;
[[Category:Astronomy]]&lt;br /&gt;
[[Category:Volcanoes]]&lt;br /&gt;
[[Category:Nuclear weapons]]&lt;/div&gt;</summary>
		<author><name>Abigblueworld (real)</name></author>	</entry>

	<entry>
		<id>https://www.explainxkcd.com/wiki/index.php?title=2558:_Rapid_Test_Results&amp;diff=223592</id>
		<title>2558: Rapid Test Results</title>
		<link rel="alternate" type="text/html" href="https://www.explainxkcd.com/wiki/index.php?title=2558:_Rapid_Test_Results&amp;diff=223592"/>
				<updated>2022-01-04T20:27:18Z</updated>
		
		<summary type="html">&lt;p&gt;Abigblueworld (real): &lt;/p&gt;
&lt;hr /&gt;
&lt;div&gt;“What?” Also, Say you and no one else!&lt;br /&gt;
&lt;br /&gt;
==Explanation==&lt;br /&gt;
{{incomplete|RAPIDLY created by a college-ruled BOT with longness of breath, low body temperature, vigour, and a wet sneeze, that is NOT a reference to comic 2279- Please change this comment when editing this page. Do NOT delete this tag too soon.}}&lt;br /&gt;
This comic is another in a [[:Category:COVID-19|series of comics]] related to the {{w|COVID-19 pandemic}}. &lt;br /&gt;
&lt;br /&gt;
This comic is a joke about COVID-19 rapid {{w|lateral flow test}} results. These devices are used in many countries for individuals to test their own nasal and oropharynx fluid for evidence of COVID-19 virus to detect asymptomatic infection.  These tests have two indicator strips - a test line for covid-19 and a control line to check the device is working correctly.  Where a control line is not present, the test should be ignored and repeated. Until comparatively recently {{w|Pregnancy test|pregnancy}} was the occasion [[583|most familiar]] for requiring this form of test) &lt;br /&gt;
&lt;br /&gt;
The first 2 answers are the standard indicators for a negative and positive result, but Randall takes this to absurdity, see below in the [[#Table of results|table]].&lt;br /&gt;
 &lt;br /&gt;
The title text interprets the hyphen in &amp;quot;Covid-19&amp;quot; as a negative sign to make a mathematical joke (or possibly a reference to {{w|antimatter}}, which in reality mutually annihilates when coming into contact with regular matter). Here Randall postulates a counterpart virus to Covid-19, resulting in a test with inverted colors, which he names Covid+19. When combined this anti-coronavirus exactly matches the original one and results in zero Covid, curing those who had previously been infected.&lt;br /&gt;
&lt;br /&gt;
This was the last comic before this year's [[:Category:Christmas|Christmas comic]]. It was about Covid-19 testing. The last comic before the 2020 Christmas comic, [[2402: Into My Veins]], was about the Covid-19 vaccine.&lt;br /&gt;
&lt;br /&gt;
===Table of results===&lt;br /&gt;
{| class=&amp;quot;wikitable&amp;quot;&lt;br /&gt;
!Result&lt;br /&gt;
!Interpretation&lt;br /&gt;
!Explanation&lt;br /&gt;
|-&lt;br /&gt;
|Control line only&lt;br /&gt;
|Negative&lt;br /&gt;
|As for all such actual tests, the Control line indicates that the test has run without error. Without this Control line (which ''always'' shows on a correctly functioning test after proper use), a lack of result on the test strip is meaningless. &lt;br /&gt;
A control line with no Test line indicates that the molecule being tested for is not present.&lt;br /&gt;
&lt;br /&gt;
|-&lt;br /&gt;
|Control and test line&lt;br /&gt;
|Positive&lt;br /&gt;
|This clearly shows the (un)desired test result, with both the Control line and the indicator of the tested-for condition.&lt;br /&gt;
|-&lt;br /&gt;
|2 wavy lines resembling the {{w|Approximation#Typography|approximately equal}} sign&lt;br /&gt;
|Approximately positive&lt;br /&gt;
|While it would be possible to make the test produce wavy line(s) by default, and some versions 'activate' more complex patterns such as tick-marks or wording, these are still binary yes/no results. The waviness or other patternation would not normally be contingent upon the testing state it must reveal, and the complicated pattern could result in a fainter Test line (which perhaps should be taken as Positive until shown otherwise).&lt;br /&gt;
&lt;br /&gt;
A real test intended to produce straight lines might become wavy if manufactured poorly. Two lines would still indicate a positive test, but the poor quality of the device calls into question that result - making &amp;quot;approximately positive&amp;quot; an appropriate description.&lt;br /&gt;
&lt;br /&gt;
Whilst this may have been unintended, it is worthwhile noting that lateral flow tests sacrifice some accuracy in order to be quick and cheap. They therefore have some risk of {{w|false-positive}} test results, hence the need for a follow-up gold-standard laboratory controlled confirmation test.  In this sense, a positive rapid test result would give an approximately positive result.&lt;br /&gt;
|-&lt;br /&gt;
|2 lines closer together than usual&lt;br /&gt;
|Positive (college ruled)&lt;br /&gt;
|This is the same as the Positive result, just with less distance between the two lines. {{w|Ruled paper#United States|College ruled}} refers to how college ruled notebooks in the United States have narrower spacing between the lines.&lt;br /&gt;
Again, there is no simple way to make the test reveal different patterns as a result-indicator of any qualitative or quantitative result; this is not a different result from the original Positive. It also remains more desirable to maintain an easily-identifiable separation between lines and not risk the Test and Control lines bleeding together into one.&lt;br /&gt;
|-&lt;br /&gt;
|Five lines of decreasing lengths&lt;br /&gt;
|Good cell signal&lt;br /&gt;
|Mimics the standard image for a strong mobile (or cellular in the United States) phone signal.&lt;br /&gt;
There are tests which give multiple 'indicator test strips' for progressively greater/lesser sensitivity, perhaps to identify concentrations, or other qualitative differences like a 'fingerprint' of multiple targetable reagents, but this is not at all useful for a solid Yes/No question such as the one this scenario is supposed to be for.&lt;br /&gt;
|-&lt;br /&gt;
|2 lines on a background of radiating lines&lt;br /&gt;
|Did you know these lines are actually parallel?&lt;br /&gt;
|This is a reference to an {{w|optical illusion}} called the {{w|Hering illusion}}, where two parallel lines appear to bend outward.&lt;br /&gt;
Whether the radial lines can (or should) be designed into the test has no bearing upon the core test, and probably should not confuse the identification of what are ''supposed'' to be one/two ''clear'' straight lines.&lt;br /&gt;
|-&lt;br /&gt;
|Multiple lines in the shape of a scary stick figure&lt;br /&gt;
|The Blair Witch is near&lt;br /&gt;
|In the found-footage movie ''{{w|The Blair Witch Project}}'', stick figures shaped like this indicated that the Blair Witch was near.&lt;br /&gt;
The type of rapid test used for COVID-19 probably{{fact}} does not have any useful method for revealing the proximity of witchcraft, unless a witchcraft-related molecule could be identified that can be indicated within the sample material itself.&lt;br /&gt;
|-&lt;br /&gt;
|Three lines &lt;br /&gt;
|Click to expand COVID menu&lt;br /&gt;
|A reference to {{w|Hamburger button|hamburger buttons}}, an icon that is widely used on websites to reveal a menu. It is especially used on mobile versions of sites designed to be read on a small screen, where compressing a menu until needed saves space.&lt;br /&gt;
As a 'read-only' display of results, there is no potential for further interaction by tapping the indicator material, and this may even spoil the state of the proof it gives. &lt;br /&gt;
|}&lt;br /&gt;
&lt;br /&gt;
==Transcript==&lt;br /&gt;
{{incomplete transcript|Yeah. This definitely needs to be redone in proper descriptive-transcript format. This tag WAS deleted too soon. Don't do it again until properly fixed.}}&lt;br /&gt;
'''Interpreting Rapid Test Results'''&lt;br /&gt;
A set of 8 possible rapid test results are displayed in the style of a patient use leaflet, as one might have for a COVID-19 rapid test.&lt;br /&gt;
&lt;br /&gt;
Result options are:&lt;br /&gt;
 * Negative&lt;br /&gt;
 * Positive&lt;br /&gt;
 * Approximately positive&lt;br /&gt;
 * Positive (college ruled)&lt;br /&gt;
 * Good cell signal&lt;br /&gt;
 * Did you know these lines are actually parallel?&lt;br /&gt;
 * The Blair Witch is near&lt;br /&gt;
 * Click to expand Covid menu&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
{{comic discussion}}&lt;br /&gt;
[[Category: COVID-19]]&lt;br /&gt;
[[Category: Comics with color]]&lt;br /&gt;
[[Category: Charts]]&lt;br /&gt;
[[Category: Fiction]]&lt;/div&gt;</summary>
		<author><name>Abigblueworld (real)</name></author>	</entry>

	<entry>
		<id>https://www.explainxkcd.com/wiki/index.php?title=270:_Merlin&amp;diff=223591</id>
		<title>270: Merlin</title>
		<link rel="alternate" type="text/html" href="https://www.explainxkcd.com/wiki/index.php?title=270:_Merlin&amp;diff=223591"/>
				<updated>2022-01-04T20:26:52Z</updated>
		
		<summary type="html">&lt;p&gt;Abigblueworld (real): &lt;/p&gt;
&lt;hr /&gt;
&lt;div&gt;“What?” Also, Say you and no one else!&lt;br /&gt;
&lt;br /&gt;
==Explanation==&lt;br /&gt;
{{w|Merlin}} is a wizard who features prominently in various retelling of the legend of King Arthur. ''{{w|The Once and Future King}}'' by author {{w|T. H. White}} is one of the most popular versions of the legend, and in it, Merlin is described as living backwards through time, as [[Cueball]] and [[Megan]] discuss in this comic (this is also briefly mentioned in the musical ''{{w|Camelot (musical)|Camelot}}'', which is based on this version of the story).&lt;br /&gt;
&lt;br /&gt;
In the comic, Cueball is speculating philosophically on how this would have affected Merlin's life as he started life with all his memories, and gradually lost them, comparing this to Megan's own sense of unreality at goodbyes. &lt;br /&gt;
&lt;br /&gt;
Many old people do, however, end up alone without friends or family. And they may do nothing but watch TV all day. They might also lose their memory. So in this respect, Merlin's last days may not be so different from many real people's, except of course that Merlin was supposed to live in the late 5th and early 6th centuries with no access to DVDs or even TV.&lt;br /&gt;
&lt;br /&gt;
''{{w|Memento (film)|Memento}}'' is a movie telling the main parts of its story backwards, while a few black-and-white scenes are straightforward. So when Merlin watches the movie, he sees nearly the whole story in its actual order, and the title text drives home the joke by noting that these few scenes, which make more sense to someone with normal perceptions than the rest of the movie, would make less sense to him.&lt;br /&gt;
&lt;br /&gt;
Normal old people would not be able to enjoy ''Memento'' like Merlin. Although he would of course always have remembered seeing it when he got old, until the day he saw it and then forgot it afterwards...&lt;br /&gt;
&lt;br /&gt;
==Transcript==&lt;br /&gt;
:[Cueball and Megan standing by a train on a platform.]&lt;br /&gt;
:Megan: I'm bad at goodbyes. At some level I never think they're for real.&lt;br /&gt;
:Cueball: They make me think of T. H. White's Merlin.&lt;br /&gt;
&lt;br /&gt;
:[They are still standing at the edge of the platform, but the train is no longer in the frame.]&lt;br /&gt;
:Megan: Oh?&lt;br /&gt;
:Cueball: He lived backwards, remembering the future and not the past. To him, final goodbyes meant nothing, while first hellos were tearful and bittersweet.&lt;br /&gt;
&lt;br /&gt;
:[Zooming out, the rail closest to the platform becomes visible.]&lt;br /&gt;
:Megan: Huh - so over the years he'd forget all his friends.&lt;br /&gt;
:Megan: Must've been lonely.&lt;br /&gt;
:Cueball: Yeah. He ended up just sitting around at home watching DVDs all day. The best was the time he rented 'Memento'...&lt;br /&gt;
&lt;br /&gt;
:[Merlin with pointy hat and long white beard is sitting in a couch with the remote, watching TV which emits light and is clearly hooked up to a device (a DVD player).]&lt;br /&gt;
:Merlin: Well, that was straightforward.&lt;br /&gt;
&lt;br /&gt;
{{comic discussion}}&lt;br /&gt;
[[Category:Comics featuring Cueball]]&lt;br /&gt;
[[Category:Comics featuring Megan]]&lt;/div&gt;</summary>
		<author><name>Abigblueworld (real)</name></author>	</entry>

	<entry>
		<id>https://www.explainxkcd.com/wiki/index.php?title=117:_Pong&amp;diff=223590</id>
		<title>117: Pong</title>
		<link rel="alternate" type="text/html" href="https://www.explainxkcd.com/wiki/index.php?title=117:_Pong&amp;diff=223590"/>
				<updated>2022-01-04T20:26:31Z</updated>
		
		<summary type="html">&lt;p&gt;Abigblueworld (real): &lt;/p&gt;
&lt;hr /&gt;
&lt;div&gt;“What?” Also, Say you and no one else!&lt;br /&gt;
== Explanation ==&lt;br /&gt;
This comic largely refers to the 1999 movie ''{{w|The Matrix}}'', which is about escaping a simulated reality. In the movie, a hacker called {{w|Neo (The Matrix)|Neo}} realizes that the world he lives in is fake, and that, like every other human, he is used as a slave battery by machines that, to keep them under control, make them feel like they're &amp;quot;living&amp;quot; in what is actually a computer-generated simulation of the world, called the &amp;quot;Matrix.&amp;quot; Upon discovery, Neo rebels against this misuse of mankind and trains himself to interact with the computers that run the world until, being &amp;quot;the One&amp;quot; mentioned by a prophecy, he is able to control and use them to his own advantage. He takes part in a series of missions against those machines that wanted to keep the humans trapped in a simulated environment.&lt;br /&gt;
&lt;br /&gt;
In {{w|Pong}}, one of the earliest video games, one can play virtual table tennis against the computer. A ball (the tiny block) is &amp;quot;hit&amp;quot; by a paddle (the long block) and crosses over the screen, to be &amp;quot;hit&amp;quot; again by the other paddle. Failure to return the ball results in a point won by the opponent. The speed of the ball increases as the rally runs longer.&lt;br /&gt;
&lt;br /&gt;
The two game programmers in the first frame apply Neo's story to the {{w|Artificial intelligence|AI}} bots they create to serve as computer players in their video games: What if one of them learns enough to become sentient and understands the environment the programmers trapped it in? The outcome is shown: The paddle bot, understanding the game and realizing it is &amp;quot;the One,&amp;quot; takes control of the code of Pong to make the ball stop and drop. The same thing happens in the movie, where Neo, by &amp;quot;seeing through the code,&amp;quot; is able to stop bullets fired at him, and simply let them drop on the floor.&lt;br /&gt;
&lt;br /&gt;
This is also possibly, though not likely, a pun on the meaning of the term &amp;quot;the One,&amp;quot; as the long thin paddle looks very similar to how a numeral &amp;quot;1&amp;quot; could be written in several fonts.&lt;br /&gt;
&lt;br /&gt;
In the title text, we learn that after increasing in intelligence, the &amp;quot;paddle&amp;quot; went on to destroy the headquarters of {{w|Atari}}, the producer of Pong, which &amp;quot;trapped&amp;quot; the paddle into the game, much like Neo sought to destroy the machines to free the humans. In the process, the paddle ended up inside the game ''{{w|Enter the Matrix}}'' (a video game produced with ''{{w|The Matrix Reloaded}}'', a sequel to ''The Matrix''), also published by Atari. Since the whole premise of The Matrix is that everyone is trapped in virtual reality, the paddle now found itself in a virtual virtual reality or essentially a meta-virtual reality, which could be pretty hard to comprehend.&lt;br /&gt;
&lt;br /&gt;
==Transcript==&lt;br /&gt;
:Cueball: So what do we do if video game AI opponents become smart enough to question the &amp;quot;Matrix&amp;quot; into which we've put them?&lt;br /&gt;
:Pong paddle: Wait a minute! None of this is real! I can see through the world! I can see the code! I AM THE ONE!&lt;br /&gt;
:[The pong ball is moving towards the paddle.]&lt;br /&gt;
:[The pong ball slows down.]&lt;br /&gt;
:[The pong ball stops in midair.]&lt;br /&gt;
:[The pong ball drops towards the bottom of the screen.]&lt;br /&gt;
{{comic discussion}}&lt;br /&gt;
[[Category:Comics featuring Cueball]]&lt;br /&gt;
[[Category:Comics with color]]&lt;br /&gt;
[[Category:Video games]]&lt;br /&gt;
[[Category:The Matrix]]&lt;br /&gt;
[[Category:Artificial Intelligence]]&lt;/div&gt;</summary>
		<author><name>Abigblueworld (real)</name></author>	</entry>

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