1. Only use launchpads if you can get a really good close call with them and if you can't get the close call in any other way. Also, you should never use launchpad chains (lots of launchpads in a line). There is simply never a need for them.
2. Avoid gold delay. It just makes the map take longer to load, and it's kind of cheap anyway.
3. When you place the enemies, you shouldn't have placed all 20 rockets on top of each other. That just makes the rockets bunch up a lot quicker, and you should always avoid letting rockets bunch up, since when rockets bunch up, it's not really 20 rockets, but just one. Don't wait until they're completely bunched up to destroy them - you should destroy them long before they're completely bunched up.
4. Try to avoid running away from the rockets. When you ran away from them, there were plenty of opportunities to get close calls by running towards the rockets and dive into the pack. Don't miss those opportunities.
5. Try using more different types of propulsion methods, as outlined in this [metanet.2.forumer.com] guide.

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To see some good examples of DDAs, search for DDAs by Clifty and bluenin. You could also watch my own "Rocket Inferno," which has 20 rockets, the same amount as this DDA. Also, try watching lord_zecrus's "34rockets" DDAs, and my "REM: Rapid Eye Movement" DDAs to see how launchpads should be used.

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the rockets bunched for too long, no close calls, too much gold delay, and too many launchpads and rockets.
1.5, but you have potential, don't let this get you down.
And sorry for being so harsh.