body {
    min-height: 100vh;
    min-height: 100dvh;
    display: flex;
    flex-direction: column;
}

/* Keep the counter vertically centered in the viewport, below the header. */
header {
    position: absolute;
    top: 0;
}

main {
    flex: 1;
    display: flex;
    align-items: center;
    justify-content: center;
    padding-block: 10rem;
}

.timer {
    text-align: center;
    min-width: 0;
    max-width: 100%;
    margin: 0;
}

.counter {
    display: flex;
    align-items: baseline;
    justify-content: center;
    max-width: 100%;
    overflow-x: auto;
    font-family: var(--pico-font-family-monospace);
    font-size: clamp(3rem, 12vw, 6rem);
    line-height: 1.2;
    margin-bottom: 1.5rem;
}

.counter input {
    box-sizing: content-box;
    flex: 0 0 auto;
    width: 1ch;
    height: auto;
    margin: 0;
    padding: 0;
    border: 0;
    border-radius: 0;
    background: transparent;
    box-shadow: none;
    color: inherit;
    font: inherit;
    line-height: inherit;
    text-align: right;
}

.counter #seconds {
    width: 2ch;
    text-align: left;
}

.counter input:focus {
    background: transparent;
    box-shadow: none;
}

.counter input:focus-visible:not([readonly]) {
    outline: 2px solid var(--pico-primary);
    outline-offset: 4px;
}

.controls {
    display: flex;
    justify-content: center;
    gap: 1rem;
}

.controls button {
    margin: 0;
    min-width: 6rem;
}

.counter.finished {
    animation: flash 1s steps(1, end) infinite;
}

@keyframes flash {
    0%, 100% { opacity: 1; }
    50% { opacity: 0; }
}

.visually-hidden {
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    overflow: hidden;
    clip-path: inset(50%);
    white-space: nowrap;
}