<snapdata remixID="8927217"><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="180" y="-120" 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="23" y="10"><block s="clear"></block></script><script x="28" y="91"><custom-block s="draw 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;        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