You change the third property of the P attribute.

Invalid friction, sometimes shortened to IF, is a glitch produced by giving a block of solid ground a bad value for friction (i.e. a negative number or a block of text). Its side effects allow the creation of new types of maps with features such as teleporting, phasing through solid ground, and delayed springboards, among other things. These are all more of features than bugs, but are technically the latter.


Any non-ground object that touches IF ground gets teleported to coordinates (0,0) and is stuck there until the end of the round. This includes mice. One application of this is putting the mouse hole slightly below (35 point below) (0,0). Then, if a mouse gets cheese then touches the IF ground, it has successfully completed the level. By this rule, potentially any solid ground could act as the mouse hole. Here is a proof-of-concept map:

Complete the map by getting the cheese, then touching the solid ground on the right.

<C><P /><Z><S><S L="175" X="766" H="89" Y="284" T="1" P="0,0,0,0.2,100,0,0,0" /><S L="175" X="757" H="89" Y="318" T="1" P="0,0,0,0.2,110,0,0,0" /><S L="175" X="743" H="89" Y="349" T="1" P="0,0,0,0.2,120,0,0,0" /><S L="175" X="723" H="89" Y="378" T="1" P="0,0,0,0.2,130,0,0,0" /><S L="175" X="698" H="89" Y="403" T="1" P="0,0,0,0.2,140,0,0,0" /><S L="175" X="670" H="89" Y="423" T="1" P="0,0,0,0.2,150,0,0,0" /><S L="175" X="638" H="89" Y="437" T="1" P="0,0,0,0.2,160,0,0,0" /><S L="175" X="604" H="89" Y="446" T="1" P="0,0,0,0.2,170,0,0,0" /><S L="175" X="571" H="89" Y="450" T="1" P="0,0,0,0.2,180,0,0,0" /><S L="175" X="536" H="89" Y="446" T="1" P="0,0,0,0.2,190,0,0,0" /><S L="175" X="502" H="89" Y="437" T="1" P="0,0,0,0.2,200,0,0,0" /><S L="175" X="471" H="89" Y="423" T="1" P="0,0,0,0.2,210,0,0,0" /><S L="175" X="442" H="89" Y="403" T="1" P="0,0,0,0.2,220,0,0,0" /><S L="175" X="417" H="89" Y="378" T="1" P="0,0,0,0.2,230,0,0,0" /><S L="175" X="397" H="89" Y="349" T="1" P="0,0,0,0.2,240,0,0,0" /><S L="175" X="383" H="89" Y="318" T="1" P="0,0,0,0.2,250,0,0,0" /><S L="175" X="374" H="89" Y="284" T="1" P="0,0,0,0.2,260,0,0,0" /><S L="55" X="363" H="66" Y="171" T="0" P="0,0,0.3,0.2,0,0,0,0" /><S L="74" X="717" H="42" Y="165" T="3" P="0,0,0,5,10,0,0,0" /><S L="56" X="113" H="61" Y="174" T="0" P="0,0,-1,0.2,0,0,0,0" /></S><D><F X="375" Y="131" /><DS X="378" Y="122" /><DC X="346" Y="124" /><T X="1" Y="35" /></D><O><O P="0" X="242" C="4" Y="79" /><O P="0" X="27" C="3" Y="85" /><O P="0" X="71" C="11" Y="85" /><O P="0" X="6" C="11" Y="84" /><O P="0" X="336" C="11" Y="78" /><O P="0" X="148" C="11" Y="79" /></O></Z></C>

Note: Once any mice hit the IF ground, the remaining mice will experience phasing (see below) if they remain on any solid ground.


IF Phasing Map

Complete the map by getting the cheese, pulling out the switch, then reaching the hole. The lava ground is actually IF.

Once an object touches IF ground, objects that remain on any solid ground will be pulled downwards, eventually with enough force that they pass through the ground. An application of this is to divide the level into (at least) two parts. The mice start up in the higher section, then, when IF activates, they phase through the ground to the lower section. Interestingly, objects (including mice) that are not in contact with any solid ground are not effected by IF activation. It follows that the lower level must be made of objects like boards, boxes, etc. instead of solid ground. Proof-of-concept map:

<C><P /><Z><S><S L="2000" X="-78" H="24" Y="302" T="0" P="0,0,0.3,0.2,0,0,0,0" /><S L="30" X="291" H="20" Y="78" T="0" P="0,0,0.3,0.2,0,0,0,0" /><S L="20" X="318" H="160" Y="147" T="0" P="0,0,0.3,0.2,0,0,0,0" /><S L="20" X="318" H="50" Y="264" T="0" P="0,0,0.3,0.2,0,0,0,0" /><S L="30" X="291" H="11" Y="283" T="3" P="0,0,-1,20,0,0,0,0" /><S L="20" X="265" H="160" Y="147" T="0" P="0,0,0.3,0.2,0,0,0,0" /><S L="20" X="265" H="50" Y="264" T="0" P="0,0,0.3,0.2,0,0,0,0" /><S L="10" X="541" H="10" Y="74" T="0" P="0,0,0.3,0.2,0,0,0,0" /><S L="10" X="555" H="10" Y="73" T="0" P="0,0,0.3,0.2,0,0,0,0" /><S L="10" X="525" H="31" Y="70" T="0" P="0,0,0.3,0.2,0,0,0,0" /><S L="38" X="549" H="10" Y="59" T="0" P="0,0,0.3,0.2,0,0,0,0" /><S L="10" X="570" H="29" Y="68" T="0" P="0,0,0.3,0.2,0,0,0,0" /><S L="43" X="549" H="10" Y="91" T="0" P="0,0,0.3,0.2,0,0,0,0" /><S L="20" X="231" H="12" Y="282" T="0" P="0,0,0.3,0.2,0,0,0,0" /></S><D><DC X="461" Y="273" /><DS X="482" Y="274" /><F X="109" Y="280" /><T X="598" Y="367" /></D><O><O P="0" X="292" C="6" Y="106" /><O P="0" X="264" C="3" Y="234" /><O P="90" X="219" C="3" Y="240" /><O P="0" X="218" C="22" Y="233" /><O P="-30" X="549" C="3" Y="107" /><O P="30" X="549" C="3" Y="106" /><O P="0" X="549" C="11" Y="108" /><O P="-20" X="609" C="4" Y="172" /><O P="15" X="565" C="3" Y="218" /><O P="-60" X="539" C="3" Y="168" /><O P="0" X="519" C="11" Y="206" /><O P="0" X="699" C="11" Y="140" /><O P="0" X="572" C="3" Y="369" /><O P="0" X="158" C="4" Y="369" /><O P="0" X="528" C="11" Y="369" /><O P="0" X="616" C="11" Y="369" /><O P="0" X="252" C="11" Y="369" /><O P="0" X="66" C="11" Y="369" /><O P="90" X="324" C="3" Y="413" /><O P="90" X="456" C="3" Y="413" /><O P="90" X="385" C="3" Y="413" /><O P="0" X="324" C="11" Y="372" /><O P="0" X="384" C="11" Y="371" /><O P="0" X="455" C="11" Y="370" /></O></Z></C>

Delayed SpringboardsEdit

When mice phase through solid ground when IF is active, they do so with great force. So, by placing a board underneath the solid ground (which must be thin), a springboard is ostensibly created. Proof-of-concept map:

If you stand on the IF ground above the board long enough, you will launched into the air. Be sure to take the right path, as the left path is a trap.

<C><P /><Z><S><S L="10" X="404" H="250" Y="118" T="0" P="0,0,0,0.2,0,0,0,0" /><S L="31" X="827" H="10" Y="58" T="0" P="0,0,asdf,0.2,0,0,0,0" /><S L="41" X="199" H="10" Y="130" T="0" P="0,0,0.3,0.2,0,0,0,0" /><S L="350" X="216" H="10" Y="354" T="0" P="0,0,0,0.2,-15,0,0,0" /><S L="100" X="540" H="10" Y="271" T="0" P="0,0,0,0.2,0,0,0,0" /><S L="10" X="331" H="202" Y="161" T="0" P="0,0,0.3,0.2,0,0,0,0" /><S L="661" X="5" H="10" Y="268" T="0" P="0,0,0.3,0.2,0,0,0,0" /><S L="53" X="73" H="10" Y="353" T="0" P="0,0,0.3,0.2,0,0,0,0" /></S><D><F X="201" Y="116" /><T X="706" Y="194" /><T X="70" Y="323" /><DS X="45" Y="54" /><DC X="45" Y="55" /></D><O><O P="0" X="120" C="4" Y="143" /><O P="0" X="213" C="11" Y="144" /><O P="0" X="29" C="11" Y="144" /><O P="0" X="819" C="6" Y="45" /><O P="-15" X="438" C="3" Y="294" /><O P="0" X="540" C="3" Y="283" /><O P="0" X="583" C="11" Y="284" /><O P="0" X="497" C="11" Y="284" /><O P="0" X="397" C="11" Y="306" /><O P="0" X="480" C="11" Y="284" /></O></Z></C>

Disabling Red Anchors Edit

IF is also used to disable red anchors in a map. Make the IF ground small (10x10), make it dynamic, set its linear damping to 9999, select fixed rotation. Place it in a location where it could not be quickly and easily reached and put red anchor in its centre. Create another ground above it that is dynamic. Adjust distance and linear damping of it so they touch (disabling red anchors) on desired moment. Keep in mind that making the distance too small may result in connection before the red anchor is spawned and nothing will happen. Proof-of-concept map:

<C><P /><Z><S><S P="0,0,0.3,0.2,0,0,0,0" L="593" H="10" X="447" Y="263" T="0" /><S P="1,0,INVALIDFRICTION,0.2,0,1,9999,0" L="10" H="10" X="0" Y="0" T="0" /><S P="1,0,0.3,0.2,0,0,1,0" L="10" H="10" X="0" Y="-12" T="0" /></S><D><T X="179" Y="254" /><F X="449" Y="250" /><DS X="724" Y="240" /><DC X="694" Y="240" /></D><O><O X="0" C="11" Y="0" P="0" /></O></Z></C>


  • If any board that's been red-nailed down is touching any solid ground, IF will not work.
  • Once a mouse has touched IF ground, teleporting it to (0,0), there is no way for it to move for the rest of the round.
  • Depending on the positioning of boards below, it's possible for a mouse to phase through solid ground and go through the board underneath as well.
  • Once IF is activated, a mouse can jump on solid ground at most once, if at all, with exception of disabling red anchor maps.