<snapdata remixID="8927081"><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" id="1"><pentrails>data:image/png;base64,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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="202" y="-150" heading="90" scale="1" volume="100" pan="0" rotation="1" draggable="true" costume="0" color="255,47,31,1" 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="255" y="34"><custom-block s="draw squares with %s rows"><l>7</l></custom-block></script><script x="18.999999000000003" y="23.999998999999946"><block s="clear"></block><block s="gotoXY"><l>-198</l><l>-150</l></block><block s="doRepeat"><l>4</l><script><custom-block s="draw black square size %n"><l>50</l></custom-block><custom-block s="draw red square size %n"><l>50</l></custom-block></script></block></script><script x="19.999999000000003" y="157.99999899999995"><block s="clear"></block><block s="gotoXY"><l>-198</l><l>-150</l></block><custom-block s="rowA"></custom-block><block s="gotoXY"><l>-198</l><l>-100</l></block><custom-block s="rowB"></custom-block></script><script x="195" y="198"><block s="clear"></block><block s="doDeclareVariables"><list><l>y value</l><l>row</l></list></block><block s="doSetVar"><l>y value</l><l>-150</l></block><block s="doSetVar"><l>row</l><l>1</l></block><block s="doRepeat"><l>7</l><script><block s="gotoXY"><l>-198</l><block var="y value"/></block><block s="doIfElse"><block s="reportEquals"><block s="reportModulus"><block var="row"/><l>2</l></block><l>1</l></block><script><custom-block s="rowA"></custom-block></script><script><custom-block s="rowB"></custom-block></script></block><block s="doChangeVar"><l>y value</l><l>50</l></block><block s="doChangeVar"><l>row</l><l>1</l></block></script></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;        break;&#xD;};&#xD;}&#xD;finally {&#xD;ide.savingPreferences = false;&#xD;};&#xD;</l></block><list><block var="which"/><block var="tf"/></list></block></script></block-definition><block-definition s="draw brick, length: %&apos;length&apos; width: %&apos;width&apos;" type="command" category="pen"><header></header><code></code><translations></translations><inputs><input type="%n"></input><input type="%n"></input></inputs><script><block s="setColor"><color>145,26,68,1</color></block><custom-block s="set flat line ends to %b"><block s="reportBoolean"><l><bool>true</bool></l></block></custom-block><block s="setSize"><block var="width"/></block><block s="down"></block><block s="forward"><block var="length"/></block><block s="up"></block></script></block-definition><block-definition s="set flat line ends to %&apos;flag&apos;" type="command" category="pen"><header></header><code></code><translations></translations><inputs><input 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