The play episode 1 link that takes up half the screen every weapon pickup is very annoying. I Click it by mistake then a new window opens. Aside from that great game.
4/5, I have some ideas for this game.
Needs Unlockable Content ... Different ships with different stats, upgrades to the stats on the ship.
Add weapons that destroy the barriers/or add opponents to destroy . Add temporary invincibility crystals, and crystals that stop the barriers movement temporarily, and crystals that give players an extra life.
Collect enough of a color crystal and you can break through a barrier of that color.
And....Create levels with different barriers and different tunnels.