Initially a movement against the increase in public transport fares , it assumed gigantic proportions , sparked by the excessive use of force by the state polices , turning into a series of huge demonstrations by groups and individuals , angry about a range of issues ( including new stadium projects for international sports events , demands on quality of public services , anger about corruption , and opposition to a constitutional amendment proposal , PEC 37 , which is interpreted by some as an attempt to curb repression of corruption ) .