I made it to Stage 43, but I would've died much sooner if it wasn't for the lag later on. I destroyed bases with Shockwave to clear half the screen and mainly stayed there waiting for Missiles and Shockwave to destroy everything. In much later stages, I focused my main gun only on enemies. My upgrade path was mainly:  Max Shockwave, but never put points in Knockback. Shockwave instantly kills enemies right next to you and can destroy bases when touching them.  Put 1 point each in Pierce and Criticals.  Max Homing Missiles, and put ~5 in Missile Burst.  Max Frenzy. The cooldown for Shockwave goes twice as fast when Frenzy is active. It'll also help you dash in to grab power-ups.  Max Pierce, Criticals, and Missile Burst.  Upgrade your main gun starting with Burst and Splitter Shells. Around Stage 30, you'll need more Speed from Fire Rate to outrun some enemies. Upgrade Accuracy last since you're depending on Criticals.
Just a few suggestions: Allow the mouse to scroll at the edges but only when you're not aiming. Possibly add a zoom. In the play menu, keep the tabs in the same order. In the weapon shop, show the weapon description on mouse-over of the weapon icon or add the ? icon.
Gimmicky button placement? When you start a new game, the "Next" x2, "Premium Goods", and "Purchase All" buttons are all in the same spot in sequential screens. A good GUI design never places buttons for different actions in the same spot where users can accidentally click on them.
A healthy break... So if I want to spend as much energy as possible without gems, that's a 3hr 20min break for 50 max energy. I'd have to wake up in the middle of the night. That doesn't seem healthy at all.