Everything is being redone compared to the old Godot 2 version. Most of the individual assets are still the same, but there are completely new materials, new logic, new objects, and new mechanics.
Among the differences
1. Some mechanics see their debut a bit earlier, the old game had powerups not being seen until the first boss level (compared to the first level here).
2. You don't just wheel into armor pieces, batteries, and other things anymore. You get them out of blocks which you break by jumping on them.
3. The special objects (that appeared when all gems are collected) are gone. In their place are special red-colored point objects. There's even a few that are only collectable if a task is completed.
4. The levels are bigger, and the camera can turn a full 360 degrees. The player can move faster too.
5. There are lives and extra life blocks now
6. Enemies that you can destroy are in
7. The UI has a new gem indicator that is more minimalist. A center circle transitions from black to red as you get close to a gem, you also get a white outline if you are moving in the direction of a gem.
8. The logic in general should be faster, the code has most logic separated into their own functions, so less code being checked at once.
The controls are mostly the same, arrows move, space jumps, but pressing space a second time with the thrusting powerup can send you down at high speed (for getting rid of enemies and smashing blocks).
Runs at a silky-smooth 60 FPS on my new GeForce GTX 1060 6GB (this is a very common card according to the statistics from Steam, very much in the mid-range, so most discrete GPU owners should see it run fine).
I did the exported builds in a Godot 3.1 dev. version (Godot itself gave no errors, so hopefully it worked). By the way, 'Totally Lost' is not dead (as I wanted to at least get a demo done to see what full use of Godot 3's new 3D engine looks like).