html,
body {
    margin: 0;
    padding: 0;
    height: 100%;
    width: 100%;
    display: flex;
    align-items: center;
    justify-content: center;
    /* use system UI font stack for best native rendering */
    font-family:
        system-ui,
        -apple-system,
        BlinkMacSystemFont,
        "Segoe UI",
        Roboto,
        "Helvetica Neue",
        Arial,
        sans-serif;
}
#app {
    text-align: center;
    width: 100%;
    max-width: 800px;
    padding: 0 2em;
}

/* Instructions screen styling */
#instructions-screen h1 {
    font-size: 6vmin;
    margin: 0.5em 0;
}
#instructions {
    font-size: 4vmin;
    line-height: 1.4;
    margin: 1.5em 0;
    padding: 0 1em;
    color: #333;
}

/* Exercise screen styling */
#exercise-screen h1 {
    font-size: 8vmin;
    margin: 0.5em 0;
}
#status {
    font-size: 6vmin;
    margin: 0.5em 0;
}
#timer {
    font-size: 12vmin;
    margin: 0.5em 0;
    font-weight: bold;
}

button {
    font-size: 6vmin;
    padding: 0.5em 1em;
    border: none;
    border-radius: 8px;
    background-color: #4a90e2;
    color: white;
    cursor: pointer;
    transition: background-color 0.2s ease;
}

button:hover {
    background-color: #357abd;
}

button:active {
    background-color: #2e6ba0;
}

/* Exercise progress bar across the top (by exercise count) */
#progress-container {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 8px;
    background-color: #ddd;
    z-index: 1000;
}
#progress-bar {
    width: 0;
    height: 100%;
    background-color: #4a90e2;
    transition: width 0.3s ease;
}