<snapdata remixID="8923318"><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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</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="120" y="140" 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="31.999999000000003" y="15.999998999999917"><block s="receiveKey"><l><option>space</option></l></block><custom-block s="draw checkerboard"></custom-block></script><script x="222" y="10"><block s="receiveKey"><l><option>right arrow</option></l></block><block s="clear"></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 type="%b"></input></inputs><script><custom-block s="set flag %s to %b"><l>Flat line ends</l><block var="flag"/></custom-block></script></block-definition><block-definition s="draw black square size %&apos;size&apos;" type="command" category="pen"><header></header><code></code><translations></translations><inputs><input type="%n"></input></inputs><script><block s="setColor"><color>8,5,0,1</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="size"/></block><block s="down"></block><block s="forward"><block var="size"/></block><block s="up"></block></script></block-definition><block-definition s="draw red square size %&apos;size&apos;" type="command" category="pen"><header></header><code></code><translations></translations><inputs><input type="%n"></input></inputs><script><block s="setColor"><color>255,47,31,1</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="size"/></block><block s="down"></block><block s="forward"><block var="size"/></block><block s="up"></block></script></block-definition><block-definition s="draw checkerboard" type="command" category="pen"><header></header><code></code><translations></translations><inputs></inputs><script><block s="gotoXY"><l>-200</l><l>-140</l></block><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><block s="gotoXY"><l>-200</l><l>-100</l></block><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><block s="gotoXY"><l>-200</l><l>-60</l></block><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><block s="gotoXY"><l>-200</l><l>-20</l></block><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><block s="gotoXY"><l>-200</l><l>20</l></block><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><block s="gotoXY"><l>-200</l><l>60</l></block><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><block s="gotoXY"><l>-200</l><l>100</l></block><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><block s="gotoXY"><l>-200</l><l>140</l></block><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></blocks><variables></variables></project><media name="U2L4-checkerboard_SV" app="Snap! 5.1, http://snap.berkeley.edu" version="1"></media></snapdata>