Progression system, polish

We've added a lot since the last update, mostly in the form of minor tweaks and bug fixes.

This build also introduces the progression system. You need to beat a level on hard difficulty or above to get a point, and each level above the first two requires at least one point to unlock. (Levels 4-7 aren't in the game yet, so they can't be unlocked currently)

The level select screen looks a lot busier now, but I think we've done a good job of conveying all the information we needed to without it getting too cluttered.

Another thing we added was in-game notifications for when you beat a level or get a new highscore:

That's about it for changes I can take a screenshot of. Other additions include:

• General polish and balance changes to all 3 levels
• New colour schemes and patterns at different difficulty levels
• Several game-breaking bugs (e.g. walls appearing in impossible patterns, the camera trying to switch perspective at the wrong time) squashed.

That's all for now, we will be running a playtest soon over on tigsource to try and gauge what people's thoughts are on the current difficulty level, so look out for a post from us over there if you might be interested in taking part in that.