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+<title>Day 23 - Advent of Code 2016</title>
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+Oh, hello! Funny seeing you here.
+
+I appreciate your enthusiasm, but you aren't going to find much down here.
+There certainly aren't clues to any of the puzzles. The best surprises don't
+even appear in the source until you unlock them for real.
+
+Please be careful with automated requests; I'm not Google, and I can only take
+so much traffic. Please be considerate so that everyone gets to play.
+
+If you're curious about how Advent of Code works, it's running on some custom
+Perl code. Other than a few integrations (auth, analytics, ads, social media),
+I built the whole thing myself, including the design, animations, prose, and
+all of the puzzles.
+
+The puzzles probably took the longest; the easiest ones were around 45 minutes
+each, but the harder ones took 2-3 hours, and a few even longer than that. A
+lot of effort went into building this thing - I hope you're enjoying playing it
+as much as I enjoyed making it for you!
+
+If you'd like to hang out, I'm @ericwastl on Twitter.
+
+- Eric Wastl
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+<body>
+<header><div><h1 class="title-global"><a href="/">Advent of Code</a></h1><nav><ul><li><a href="/2016/about">[About]</a></li><li><a href="/2016/support">[AoC++]</a></li><li><a href="/2016/events">[Events]</a></li><li><a href="/2016/settings">[Settings]</a></li><li><a href="/2016/auth/logout">[Log Out]</a></li></ul></nav><div class="user">Neil Smith <span class="supporter">(AoC++)</span> <span class="star-count">46*</span></div></div><div><h1 class="title-event"> <span class="title-event-wrap">0xffff&</span><a href="/2016">2016</a><span class="title-event-wrap"></span></h1><nav><ul><li><a href="/2016">[Calendar]</a></li><li><a href="/2016/leaderboard">[Leaderboard]</a></li><li><a href="/2016/stats">[Stats]</a></li><li><a href="/2016/sponsors">[Sponsors]</a></li></ul></nav></div></header>
+
+<div id="sidebar">
+<div id="sponsor"><div class="quiet">Our <a href="/2016/sponsors">sponsors</a> help make AoC possible:</div><p><a href="https://info.esparklearning.com/join-our-team-full-stack-engineer" target="_blank" onclick="if(ga)ga('send','event','sponsor','click',this.href);">eSpark Learning</a> - Solve the greatest puzzle of our day - transform education</p></div>
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+
+<main>
+<article class="day-desc"><h2>--- Day 23: Safe Cracking ---</h2><p>This is one of the top floors of the nicest tower in EBHQ. The Easter Bunny's private office is here, complete with a safe hidden behind a painting, and who <em>wouldn't</em> hide a star in a safe behind a painting?</p>
+<p>The safe has a digital screen and keypad for code entry. A sticky note attached to the safe has a password hint on it: "eggs". The painting is of a large rabbit coloring some eggs. You see <code>7</code>.</p>
+<p>When you go to type the code, though, nothing appears on the display; instead, the keypad comes apart in your hands, apparently having been smashed. Behind it is some kind of socket - one that matches a connector in your <a href="11">prototype computer</a>! You pull apart the smashed keypad and extract the logic circuit, plug it into your computer, and plug your computer into the safe.</p>
+</p>Now, you just need to figure out what output the keypad would have sent to the safe. You extract the <a href="12">assembunny code</a> from the logic chip (your puzzle input).</p>
+<p>The code looks like it uses <em>almost</em> the same architecture and instruction set that the <a href="12">monorail computer</a> used! You should be able to <em>use the same assembunny interpreter</em> for this as you did there, but with one new instruction:</p>
+<p><code>tgl x</code> <em>toggles</em> the instruction <code>x</code> away (pointing at instructions like <code>jnz</code> does: positive means forward; negative means backward):</p>
+<ul>
+<li>For <em>one-argument</em> instructions, <code>inc</code> becomes <code>dec</code>, and all other one-argument instructions become <code>inc</code>.</li>
+<li>For <em>two-argument</em> instructions, <code>jnz</code> becomes <code>cpy</code>, and all other two-instructions become <code>jnz</code>.</li>
+<li>The arguments of a toggled instruction are <em>not affected</em>.</li>
+<li>If an attempt is made to toggle an instruction outside the program, <em>nothing happens</em>.</li>
+<li>If toggling produces an <em>invalid instruction</em> (like <code>cpy 1 2</code>) and an attempt is later made to execute that instruction, <em>skip it instead</em>.</li>
+<li>If <code>tgl</code> toggles <em>itself</em> (for example, if <code>a</code> is <code>0</code>, <code>tgl a</code> would target itself and become <code>inc a</code>), the resulting instruction is not executed until the next time it is reached.</li>
+</ul>
+<p>For example, given this program:</p>
+<pre><code>cpy 2 a
+tgl a
+tgl a
+tgl a
+cpy 1 a
+dec a
+dec a
+</code></pre>
+<ul>
+<li><code>cpy 2 a</code> initializes register <code>a</code> to <code>2</code>.</li>
+<li>The first <code>tgl a</code> toggles an instruction <code>a</code> (<code>2</code>) away from it, which changes the third <code>tgl a</code> into <code>inc a</code>.</li>
+<li>The second <code>tgl a</code> also modifies an instruction <code>2</code> away from it, which changes the <code>cpy 1 a</code> into <code>jnz 1 a</code>.</li>
+<li>The fourth line, which is now <code>inc a</code>, increments <code>a</code> to <code>3</code>.</li>
+<li>Finally, the fifth line, which is now <code>jnz 1 a</code>, jumps <code>a</code> (<code>3</code>) instructions ahead, skipping the <code>dec a</code> instructions.</li>
+</ul>
+<p>In this example, the final value in register <code>a</code> is <code>3</code>.</p>
+<p>The rest of the electronics seem to place the keypad entry (the number of eggs, <code>7</code>) in register <code>a</code>, run the code, and then send the value left in register <code>a</code> to the safe.</p>
+<p><em>What value</em> should be sent to the safe?</p>
+</article>
+<p>Your puzzle answer was <code>14346</code>.</p><article class="day-desc"><h2>--- Part Two ---</h2><p>The safe doesn't open, but it <em>does</em> make several <span title="SUCH INCORRECT! VERY LOCK! WOW!">angry noises</span> to express its frustration.</p>
+<p>You're quite sure your logic is working correctly, so the only other thing is... you check the painting again. As it turns out, colored eggs are still eggs. Now you count <code>12</code>.</p>
+<p>As you run the program with this new input, the prototype computer begins to <em>overheat</em>. You wonder what's taking so long, and whether the lack of any instruction more powerful than "add one" has anything to do with it. Don't bunnies usually <em>multiply</em>?</p>
+<p>Anyway, <em>what value</em> should actually be sent to the safe?</p>
+</article>
+<p>Your puzzle answer was <code>479010906</code>.</p><p class="day-success">Both parts of this puzzle are complete! They provide two gold stars: **</p>
+<p>At this point, you should <a href="/2016">return to your advent calendar</a> and try another puzzle.</p>
+<p>If you still want to see it, you can <a href="23/input" target="_blank">get your puzzle input</a>.</p>
+<p>You can also <span class="share">[Share<span class="share-content">on
+ <a href="https://twitter.com/intent/tweet?text=I%27ve+completed+%22Safe+Cracking%22+%2D+Day+23+%2D+Advent+of+Code+2016&url=http%3A%2F%2Fadventofcode%2Ecom%2F2016%2Fday%2F23&related=ericwastl&hashtags=AdventOfCode" target="_blank">Twitter</a>
+ <a href="https://plus.google.com/share?url=http%3A%2F%2Fadventofcode%2Ecom%2F2016%2Fday%2F23" target="_blank">Google+</a>
+ <a href="http://www.reddit.com/submit?url=http%3A%2F%2Fadventofcode%2Ecom%2F2016%2Fday%2F23&title=I%27ve+completed+%22Safe+Cracking%22+%2D+Day+23+%2D+Advent+of+Code+2016" target="_blank">Reddit</a
+></span>]</span> this puzzle.</p>
+</main>
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