I play a lot of NES tetris, so this actually threw my instincts for a loop. What I think is most satisfying is when I pull off a "tetris", i.e. get 4 lines at a time with a long-bar. This implementation seems greedier, as it seems to want to give you the pieces necessary to complete any line at all.

I worked around it until I got a well on the right hand side, at which point all I got was long-bars. This is the cleanest path I could find to an infinite run of tetrises: ذටරऍƐඥժݹߝɿඍݷ౫ටฅڝ௨పໃܡ௨ඖІݮ௨ഗƊݹɷඝܘܢ௨پܘݓ௨ಮІܦ௨ชІݶΗʈາђடටවݹदඦܘݣ௨ಬໃƎௐڌໃݷಒටԠђௐڊಸݹࠂƣຜࡁரڀฮࡁਓȺಥɜਆ