|N version||1.4 and later|
Run to the right, but let go before sliding down the \ slope closest to the start. On falling, you hit the next / slope just below halfway down the level, then do a single jump up which should take you above the corner of the triangle and above the rocket. Fall down and to the right to land on the \ slope; do a running jump from that to the wall to your right while grabbing the switch, walljump to the wall above you on the left, walljump from that to the / slope on the right, run up it and perpendicular jump to the wall on your left and jump to the exit.
To get the gold, go down and to the left at the start. Jump between the mines two or three at a time; do it fast enough, and the rockets won't be a problem. At the end, jump from the bottom right to the \ slope and the wall and continue as before to the exit.