When you start this stage, you will see two Kick Bombs in front of you, which act just like their name. You can’t pick them up at all, and they only move whenever you make contact with them, going in the direction in which you’re moving. There is a cannon on the ledge above the initial area, which will be spewing out more Kick Bombs. Ignore those and go straight for the Green Star ring, which will spawn green coins upon passing through it. Collect all eight coins to spawn Green Star #1. The ?-Blocks to the right of the one cannon contains a power-up (Super Bell if you are Super Mario). If you have the Cat Suit, you can climb the back wall here for a clock to add to the time.
Ride the moving platforms over the gap to the right, then knock one of the Kick Bombs into the wall to the right, revealing the Stamp. Now climb up the wall above the Stamp and hit the Cat Wheel to raise the platform. Climb to the top and jump across to the right to find Green Star #2. If you drop down from here you can land atop some Thwomps to find more clock pickups. Continue up the pathway and defeat the tower of Goombas to get Green Star #3, then continue to the final area before the boss fight. Use the Kick Bombs to blast away the back wall and reach the Warp Box. Remember that Kick Bombs flashing red will explode and damage you if you touch them.
Highway Showdown with Bowser
Bowser rides in his vehicle tossing Kick Bombs at you but you can kick them back to deal damage. Direct hits to Bowser deal more damage than hitting the vehicle but either way is effective. You need to watch out for the Kick Balls that are about to explode (flashing red) and the lava pools that Bowser will spew onto the path. If you move through this battle long enough, the scenery will change a bit and Goombas join the fray. Land several hits on Bowser or the vehicle to end the battle, then use the Warp Box to reach the final area.
Claim the clock to add to the timer and jump atop the Goal Pole to save the Sprixie Princess. She will create a pipe to access World 2 if you haven’t already used the secret exit in World 1-2.