:root {
    --bg: #1e40af;
    --card: #ffffff;
    --primary: #3b82f6;
    --primary-hover: #2563eb;
    --border: #cbd5e1;
    --text: #0f172a;
    --muted: #64748b;
    --radius: 16px;
    --shadow: 0 25px 60px rgba(0, 0, 0, .18);
}


/*  RESET */

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: system-ui, Segoe UI, sans-serif;
}

body {
    background: var(--bg);
    min-height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    padding: 30px;
    color: var(--text);
}


/* LAYOUT*/

.app {
    width: 100%;
    max-width: 520px;
}


/* CARD */

.tool {
    background: var(--card);
    padding: 38px;
    border-radius: var(--radius);
    box-shadow: var(--shadow);
    display: flex;
    flex-direction: column;
    gap: 22px;
    animation: fade .4s ease;
}

@keyframes fade {
    from {
        opacity: 0;
        transform: translateY(20px)
    }
    to {
        opacity: 1;
        transform: translateY(0)
    }
}


/* HEADER */

.tool-header h1 {
    font-size: 26px;
}

.subtitle {
    font-size: 14px;
    color: var(--muted);
    margin-top: 6px;
}


/* UPLOAD BOX */

.upload-box {
    border: 2px dashed var(--border);
    border-radius: 14px;
    padding: 40px;
    text-align: center;
    cursor: pointer;
    background: #f8fafc;
    transition: .25s;
}

.upload-box:hover {
    border-color: var(--primary);
    background: #eff6ff;
}

.upload-box input {
    display: none;
}


/* INPUT GRID */

.size-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 18px;
}

.field label {
    display: block;
    font-size: 13px;
    font-weight: 600;
    margin-bottom: 6px;
}

input {
    width: 100%;
    padding: 12px;
    border-radius: 10px;
    border: 1px solid var(--border);
    font-size: 14px;
    outline: none;
    transition: .2s;
}

input:focus {
    border-color: var(--primary);
    box-shadow: 0 0 0 3px rgba(59, 130, 246, .15);
}


/*  BUTTON */

.btn {
    padding: 16px;
    border: none;
    border-radius: 14px;
    background: var(--primary);
    color: white;
    font-size: 16px;
    font-weight: 600;
    cursor: pointer;
    transition: .25s;
}

.btn:hover {
    background: var(--primary-hover);
    transform: translateY(-1px);
}

.btn:active {
    transform: scale(.98);
}


/* PREVIEW BOX */

.preview {
    border: 1px dashed var(--border);
    padding: 18px;
    border-radius: 12px;
    background: #f9fafb;
    text-align: center;
    font-size: 14px;
    color: var(--muted);
}


/* MOBILE */

@media(max-width:480px) {
    .tool {
        padding: 26px;
    }
    .tool-header h1 {
        font-size: 22px;
    }
    .size-grid {
        grid-template-columns: 1fr;
    }
}