 Blek is a puzzle game in which the player draws a " snake @-@ like " black line on the screen that is recorded and played back like a pattern , recurring repeatedly across the screen . The object is to draw a line that it will remove colored dot targets when it repeats across the screen without hitting a black dot . Lines that travel off the top or bottom of the screen reset the level , while lines that travel off the left or right of the screen reflect back towards the dots . Aside from repeating the player 's drawn pattern , the stroke mimics the player 's pace in drawing the stroke . The game begins with no prompt or tutorial other than to use a finger on the screen and experiment . The first puzzles are " on open , white canvasses " where the player can solve the simple puzzles " by accident " . The 80 levels progress in difficulty and require more complex solutions . Added elements include a " chain reaction " dot that launches other dots when struck . Its sound consists of a " whoosh " that accompanies the traveling stroke , a " chime " when colored dots are hit , and a human " disappointed grumble " when black dots are hit , resetting the level . The game is depicted in flat , plain colors , with no pause feature and no option menu other than Game Center achievements . Players navigate between puzzles using three small onscreen icons . There are no in @-@ app purchases or in @-@ game advertisements . 
