Work/startonlevel

Activities with bar.level in the code for logic (we need to be careful when it started at 1 and now starts at 0):

• melody
• align4_2players
• gnumch
• tic_tac_toe
• babymatch activities
• bargame
• color_mix
• explore_world/animals/music
• analog/digital_electricity (we use the level to check the results)
• solar_system (even if we don't use the level directly, there is some logic for it in Quiz)
• categorization (same as solar system, we just need to double check it still works)
• railroad (more changes than expected)