Build 24: revised powerups

What’s new:

• Powerups are now grey blocks with special (programmer art) symbols, particle effect was removed. You can activate powerups immediately by tapping them instead of including them in a combo (as they can’t be included in a combo anymore).
• Powerup effect lengths were halved (to 30 seconds), but they spawn more frequently.

We’re slowly winding down post-jam development, but the plan is to add a few more mechanics (wildcard blocks, colour changing blocks and difficulty selection) plus some UI enhancements this week.