Make some levels with two or more centers of gravity.

Add a speedrun button on the play menu that will start a counter, then present all the levels in sequence with no dialog and stop the counter after the last, saving the time as high-score

• Objects hitting the black hole should shrink
• Delay victory popups to show the last planets destroyed
• Briefly pause the game on big impacts to make them more memorable moments
• Make it more clean which moon is yours and which moons are allies; can complementary colors help?
• After running out of moon, make the game give a warning sound, and require you to click on a button near the edge of the screen somewhere to acknowledge that you want to give up.
• In case you make your moon lose its orbit and hit the black hole, I would prefer something like «Your moon was swallowed by the black hole»
• Pass the text through a grammar checker
• Maybe make things slower
• Vary the pitch of explosions
• Bullets hitting the black hole should not explode
• Better black hole animation.
• Screen shake on hits.
• Particle trails on celestial bodies.
• Better health bar, with some animations.
• New stars pops up with rotating and scaling animations.

Create asteroids and add a few level with asteroid belts.

TODO:

• Reach 32 levels (4 pages)
• Adjust the requirements for 2 and 3 stars
• Adjust the levels difficulty to better fit the learning curve
• Have a moon that shoots from two opposite nozzles at the same time.
• Make some levels with two or more centers of gravity.
• Recharge the remaining shoots when destroying an enemy planet.
• Make certain planets protected by a shield, so that you need to destroy certain planets first to disable the shield's generators.
• On the late levels, planets can shoot back at you, but the enemies' shooting animations must be clear to give the player time to react
• On Level 6, the two moons orbit so close that it's difficult to distinguish which one is yours.
• Level 7 is very hard

Not viable on mobile

• Have some levels with multiple moons that can shoot and let the player cycle through moons by pressing a button.
• Have some levels where the player aims and shoots from all the moons at the same time to add a strategic challenge.

Implemented

• Maybe the nozzle can also work as a propeller, either with a secondary button that only propels, or as a side effect of shooting moons.
• Make the mass of planets variable, so that some of them are light and need to be precisely pushed in the right direction, while other are more massive and need several pushes (or a clever collision with other planets) to be sent to the black hole.
• Have some artificial planets that break into 2/3/4 pieces when hit, that get ejected around.

Populate the Option menu with the sound and music volume settings.

Add some icons with the current key bindings on the bottom of the screen.
Then disable the intro in case of failure and instead make the icons flash red.
Also expand the screen area for better use of the screen.

• The planet Earth bends in the background when modulated to red on hits.

• On Level 6, the two moons orbit so close that it's difficult to distinguish which one is yours.

• Level 7 is very hard

• If a planet is stuck to another for more than a second, nudge them away

• Remove quitting by back button on main menu

• Level 9 needs more asteroids

• Add on-screen icons that show which inputs match to which control (shoot, propel, restart, quit)

Try aiming with a cross-hair that shots at direction (crosshair - moon)

Address the complains about the music in the game:

• The music felt a little too slow/down-tempo for the game play
• The music is too grating
• The music needs a bit of variety

Feedback from the game jam

• Polish
  • Make the asteroids and mini-moons spin by a random factor
• Writing
  • More Lagrange and Kepler puns like «it's time to turn this three-body problem into a two-body solution» etc
  • The game ends a bit abruptly. A separate screen for the ending or credits would be nice
  • The ending could be improved with some flavor text
  • A little bit more of an introduction explaining how to play and you've got a great game here
• Gameplay
  • Initialize all random number generators by seed
  • Make game speed variable per level to allow early levels to be slower and later levels to be faster
  • People thinks it's difficult to get 3 stars: should it be easier to get 3 stars or make it clear that those are only for a single shot win?
  • There were a few times I got a direct hit and thought, "Yeah!" only for the planets to be unaffected. I would have liked a tiny invisible nudge when you make contact just to help feedback
  • Reorder the levels to adjust the difficulty curve
  • Adjust the requirements for 2 and 3 stars for each level
• Audio
  • Sounds are OK, except for the one that plays constantly after you shoot all your mini-moons and the menu beeps
  • The music felt a little too slow/down-tempo for the game play
  • The music was grating
  • Music needs a bit of variety

Create music for the game.

Add a score at the end of each level with the 3-stars system, but use moons instead of stars.

The star rating system only gives 3 stars for single shoot, two stars for double shoot and 1 star for more than 2 shoots.
Let's make it more fair.

Create planets that have moons orbiting around them: that will make it more difficult to take them out since the moons act as a shield.

Add story panels that help the player getting into the game and that serve as a mini tutorial at the early stages.

Address feedback on writing the game story:

• More Lagrange and Kepler puns like «it's time to turn this three-body problem into a two-body solution» etc
• The game ends a bit abruptly. A separate screen for the ending or credits would be nice
• The ending could be improved with some flavor text
• A little bit more of an introduction explaining how to play and you've got a great game here

Don't load the save file if it doesn't exist or if it's for an older version (add versions).
There is no sound in html5.
Add a fullscreen button in the options.

When there are enough levels (16 or 20?) add a grid that show each level as enabled/disabled with the 3-star rating as the score.
The player should be able to choose a level directly to improve the scoring.

Implement the touchscreen and controller game play modes to make the game playable in Android.