Why it's not so hard
I beat all 3 of the first levels (1a, 1b, 1c) and also 2a. This game SEEMS hard because you do die a fair amount. BUT, if you know a few things about the game it becomes easier:
1. You apparently have infinite lives. You die, you get to start again, and you keep your weapon upgrades from before you died. It also helps to pick the redhead in the beginning since she has more life than the others.
2. Not all weapons are created equal. Weapons like the laser or the machine gun that just shoot straight ahead basically suck. The best weapon for the first level is the missiles (3 missiles shoot, track onto target). Once you get a good weapon, keep using it (don't pick up weapon change powerups) and your weapon will upgrade permanently. By the way, you can hold 2 weapons at the same time (press d to switch to your alternate weapon) so if you find a weapon powerup that you like but don't want to use right now, you can press d, pick it up into your alternate slot, then press d again to switch back to your main weapon.
3. Use your shield (press s) if you are about to get hit by a bullet. Shield only lasts for a moment so press it right before you get hit. If your shield blocks a bullet your EMP charges up.
4. Kill as many enemies as you can BEFORE they get close. The goal of killing enemies is to prevent them from filling the air with bullets, so ideally you want to kill them before they even appear on the screen (good weapons like missiles will do this). If there is a huge bunch of enemies in the middle of the screen shooting at you, don't stand in front of them trying to kill them, focus on avoiding their bullets.