A combo star is awarded for finishing the level with 100% combo. On some longer levels with checkpoints you can bail and start your combo back up again at the checkpoint. As long as the 100% combo star at the side reads ACTIVE you will get a star at the end of a level. If you lose your combo after a checkpoint you can press to reload the last checkpoint and start your combo up again. To maintain a combo you will need to be in an almost constant manual by holding back the . You can still hold down to duck under hurdles when in a manual. You can also manual in place to recharge your boost without losing your combo if you need to.