Fill the Measure
Rhythm Invaders is a free, browser-based arcade game that turns one of the building blocks of music — note values and time signatures — into a fast Space Invaders-style shooter. Note "invaders" descend from the top of the screen, each worth a certain number of beats, and you move your launcher and fire to catch them and fill the measure. Hit the exact number of target beats to clear a wave, but don't overfill — a note bigger than the space left is a miss. It's a fun, hands-on way to build an instant feel for how beats add up.
Understanding note values and how they fit into a measure is fundamental to reading and performing music. Rhythm Invaders makes that practice exciting and game-like — perfect for music students, band and orchestra members, piano learners, and music theory classes working on rhythm and counting.
Use the left and right arrow keys to move your launcher and the spacebar to fire (on mobile, hold the left or right side of the screen to move and auto-fire). Catch the descending notes to add their beat values to your measure, hit the target exactly to clear the wave, and don't let the invaders reach the bottom. Three difficulty levels let you start gentle and work up to a real challenge.
In common 4/4 time, where each measure holds four beats:
A time signature is the pair of numbers at the start of a piece of music that tells you how beats are grouped. The top number says how many beats are in each measure, and the bottom number says which note value gets one beat. In 4/4 (the most common, often called "common time"), there are four quarter-note beats per measure. In 3/4 — waltz time — there are three. Learning to "fill the measure" correctly, exactly what Rhythm Invaders trains, is the heart of reading rhythm.