Young Star
This is a clean game with smooth animation although there are not many graphical figures, those which exist are at a high standard. The split second explosion of the enemy ships is very good; makes each kill more satisfying.
The music is also good. It's a fast track that sounds spacey and action fuelled. The sound effects are spot on and are delicate on the ears.
But the gameplay is extremely limited. The thought of a RPG like defence game came into my mind when playing this. If you look at prime examples like "storm the house 3" you can see how your game can be made similar.
Use the score, or another count up bar as money. Set a spawn rate and use it as a wave {eg 50 ships, 1 appearing every 0.5 seconds} and increase this rate per wave. After a wave the money collected could be used to increase the power of your main turret or build others turrets {that fire machine gun bullets, weaker but faster, of explosives causing splash damage}.
Upgrades to life and armour are important and the basic "increase fire rate" or "increase damage per shot" should be added. As the waves progress you may want to add new enemy spaceships which have more life, defence and stronger attackers.
What is crucial is to perhaps allow control of the movement of the turret. This would put allow more professional players to save up money for better weapons but manually avoid ships whereas the main turret would be statistically too weak if it was static. Also apply difficulty modes for a range of skills.
This is a very smooth game though. It doesn't need to be better, just a lot bigger. Graphics and sound are imprinted in this perfectly - now you need to create bigger, and more tactical, experience.