ides ▁of ▁various ▁types ▁are ▁set ▁around ▁a ▁specific ▁theme . ▁ ▁Park s ▁contains ▁a ▁mixture ▁of ▁attra ctions ▁which ▁can ▁be ▁divided ▁into ▁several ▁categories . ▁ ▁Fl at ▁r ides ▁Fl at ▁r ides ▁are ▁usually ▁considered ▁to ▁be ▁those ▁that ▁move ▁their ▁passengers ▁in ▁a ▁plane ▁generally ▁parallel ▁to ▁the ▁ground . ▁ ▁There ▁is ▁a ▁core ▁set ▁of ▁flat ▁r ides ▁which ▁most ▁am usement ▁par ks ▁have , ▁including ▁the ▁enter prise , ▁t ilt - a - wh irl , ▁gravit ron , ▁chair swing , ▁swing ing ▁in verter ▁ship , ▁tw ister , ▁and ▁top ▁spin . ▁However , ▁there ▁is ▁constant ▁innov ation , ▁with ▁new ▁variations ▁on ▁ways ▁to ▁spin ▁and ▁throw ▁passengers ▁around ▁appearing ▁in ▁an ▁effort ▁to ▁keep ▁attract ing ▁customers . ▁Man ufact ures ▁such ▁as ▁H uss ▁and ▁Zam per la ▁special ise ▁in ▁creating ▁flat ▁r ides ▁among ▁other ▁am usement ▁attra ctions . ▁ ▁Rol ler ▁co aster s ▁ ▁Am usement ▁par ks ▁often ▁feature ▁multiple ▁roll er ▁co aster s ▁of ▁primarily ▁tim ber ▁or ▁steel ▁construction . ▁Fund ament ally , ▁a ▁roll er ▁co aster ▁ride ▁is ▁one ▁in ▁which ▁a ▁special ized ▁rail road ▁system ▁with ▁ste ep ▁dro ps ▁and ▁sharp ▁curves , ▁passengers ▁sit ▁and ▁are ▁rest rained ▁in ▁cars , ▁usually ▁with ▁two ▁or ▁more ▁cars ▁joined ▁to ▁form ▁a ▁train . ▁Some ▁roll er ▁co aster s ▁feature ▁one ▁or ▁more ▁in versions ▁( such ▁as ▁vertical