<snapdata remixID="8927639"><project name="U2L4-checkerboard_SV" app="Snap! 5.1, http://snap.berkeley.edu" version="1"><notes></notes><thumbnail>data:image/png;base64,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</thumbnail><stage name="Stage" width="480" height="360" costume="0" color="255,255,255,1" tempo="60" threadsafe="false" volume="100" pan="0" lines="flat" ternary="true" codify="false" inheritance="false" sublistIDs="false" scheduled="false" 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</pentrails><costumes><list struct="atomic" id="2"></list></costumes><sounds><list struct="atomic" id="3"></list></sounds><variables></variables><blocks></blocks><scripts></scripts><sprites><sprite name="Sprite" idx="1" x="-150" y="190" heading="90" scale="1" volume="100" pan="0" rotation="1" draggable="true" costume="0" color="8,5,0,1" pen="tip" id="8"><costumes><list struct="atomic" id="9"></list></costumes><sounds><list struct="atomic" id="10"></list></sounds><blocks></blocks><variables></variables><scripts><script x="20" y="20"><block s="clear"></block></script><script x="20" y="56"><custom-block s="draw black square size %n"><l>40</l></custom-block></script><script x="20" y="95"><custom-block s="draw red square size %n"><l>40</l></custom-block></script><script x="20" y="134"><custom-block s="Make checker board"></custom-block></script></scripts></sprite></sprites></stage><hidden></hidden><headers></headers><code></code><blocks><block-definition s="set flag %&apos;which&apos; to %&apos;tf&apos;" type="command" category="sensing"><header></header><code></code><translations></translations><inputs><input type="%s" readonly="true"><options>Presentation mode&#xD;Retina display support&#xD;Long form input dialog&#xD;Plain prototype labels&#xD;Input sliders&#xD;Execute on slider change&#xD;Clicking sound&#xD;Turbo mode&#xD;Flat design&#xD;Keyboard editing&#xD;Table support&#xD;Table lines&#xD;Visible stepping&#xD;Thread safe scripts&#xD;Prefer smooth animations&#xD;Flat line ends&#xD;Codification support&#xD;Inheritance support</options></input><input type="%b"></input></inputs><script><block s="doRun"><block s="reportJSFunction"><list><l>which</l><l>tf</l></list><l>var   stage = this.parentThatIsA(StageMorph),&#xD;        ide = stage.parentThatIsA(IDE_Morph),&#xD;        world = stage.parentThatIsA(WorldMorph);&#xD;&#xD;if (tf != !!tf) return;&#xD;&#xD;try{&#xD;ide.savingPreferences = false;&#xD;&#xD;switch (which) {&#xD;    case &apos;Presentation mode&apos;:&#xD;        if (tf != ide.isAppMode) ide.toggleAppMode();&#xD;        break;&#xD;    case &apos;Retina display support&apos;:&#xD;        if (tf != isRetinaEnabled()) ide.toggleRetina();&#xD;        break;&#xD;    case &apos;Long form input dialog&apos;:&#xD;        if (tf != InputSlotDialogMorph.prototype.isLaunchingExpanded)&#xD;            ide.toggleLongFormInputDialog();&#xD;        break;&#xD;    case &apos;Plain prototype labels&apos;:&#xD;        if (tf != BlockLabelPlaceHolderMorph.prototype.plainLabel)&#xD;            ide.togglePlainPrototypeLabels();&#xD;        break;&#xD;    case &apos;Input sliders&apos;:&#xD;        MorphicPreferences.useSliderForInput = tf;&#xD;        break;&#xD;    case &apos;Execute on slider change&apos;:&#xD;        ArgMorph.prototype.executeOnSliderEdit = tf;&#xD;        break;&#xD;    case &apos;Clicking sound&apos;:&#xD;        if (tf != !!BlockMorph.prototype.snapSound)&#xD;            BlockMorph.prototype.toggleSnapSound();&#xD;        break;&#xD;    case &apos;Turbo mode&apos;:&#xD;        if (tf != stage.isFastTracked)&#xD;            ide.toggleFastTracking();&#xD;        break;&#xD;    case &apos;Flat design&apos;:&#xD;        if (tf == MorphicPreferences.isFlat) break;&#xD;        if (tf)&#xD;            ide.flatDesign();&#xD;        else&#xD;            ide.defaultDesign();&#xD;        break;&#xD;    case &apos;Keyboard editing&apos;:&#xD;            ScriptsMorph.prototype.enableKeyboard = tf;&#xD;        break;&#xD;    case &apos;Table support&apos;:&#xD;            List.prototype.enableTables = tf;&#xD;        break;&#xD;    case &apos;Table lines&apos;:&#xD;                TableMorph.prototype.highContrast = tf;&#xD;        break;&#xD;    case &apos;Visible stepping&apos;:&#xD;        if (tf != Process.prototype.enableSingleStepping)&#xD;            ide.toggleSingleStepping();&#xD;        break;&#xD;    case &apos;Thread safe scripts&apos;:&#xD;        stage.isThreadSafe = tf;&#xD;        break;&#xD;    case &apos;Prefer smooth animations&apos;:&#xD;        if (tf != (StageMorph.prototype.frameRate &gt; 0))&#xD;            ide.toggleVariableFrameRate();&#xD;        break;&#xD;    case &apos;Flat line ends&apos;:&#xD;        SpriteMorph.prototype.useFlatLineEnds = tf;&#xD;        break;&#xD;    case &apos;Codification support&apos;:&#xD;        if (tf != StageMorph.prototype.enableCodeMapping) {&#xD;            StageMorph.prototype.enableCodeMapping = tf;&#xD;            ide.currentSprite.blocksCache.variables = null;&#xD;            ide.currentSprite.paletteCache.variables = null;&#xD;            ide.refreshPalette();&#xD;        }&#xD;        break;&#xD;    case &apos;Inheritance support&apos;:&#xD;        if (tf != StageMorph.prototype.enableInheritance) {&#xD;            StageMorph.prototype.enableInheritance = tf;&#xD;            ide.currentSprite.blocksCache.variables = null;&#xD;            ide.currentSprite.paletteCache.variables = null;&#xD;            ide.refreshPalette();&#xD;        }&#xD;        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s="setSize"><block var="size"/></block><block s="down"></block><block s="forward"><block var="size"/></block><block s="up"></block></script></block-definition><block-definition s="Row A" type="command" category="pen"><header></header><code></code><translations></translations><inputs></inputs><script><block s="doRepeat"><l>4</l><script><custom-block s="draw black square size %n"><l>40</l></custom-block><custom-block s="draw red square size %n"><l>40</l></custom-block></script></block></script></block-definition><block-definition s="Row B" type="command" category="pen"><header></header><code></code><translations></translations><inputs></inputs><script><block s="doRepeat"><l>4</l><script><custom-block s="draw red square size %n"><l>40</l></custom-block><custom-block s="draw black square size %n"><l>40</l></custom-block></script></block></script></block-definition><block-definition s="Make checker board" type="command" 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